Pass it on
You both get up to €8 off.
On Zero Waste your first month is free, or two if you keep your number. UNDO is a Belgian mobile operator on Orange’s 5G network, from €4 a month.
Your discount
How you both get up to €8
The discount is €4 per monthly bill: one month with a new number, two months if you keep your number. Whoever referred you gets the same.
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New to UNDO
Switch and get up to €8 off: €4 with a new number, 2 × €4 if you keep your number. On Zero Waste that’s your first month free, or two. On Rise, Boost and Wild the same amount comes off your bill.
Choose your plan →
How it works
Three steps, one email
No code to enter when you order. We sort the discount out afterwards.
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Order online
Every plan counts. You identify yourself with itsme. An eSIM is usually active within the hour, a physical SIM card is shipped within 1 working day and usually delivered by courier within 2 working days.
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Email us once your number works
Send an email to support@undo.be with your mobile number and that of the person who referred you. Without that email we can’t apply the discount. Do this within 30 days of your number becoming active.
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We take care of the rest
We check your connection and put the discount on both your next bills after your email.
Plans
Four plans, the discount applies to each
With every plan
- What you have left, you keep
- Your full bundle, in the EU too
- You keep your number
- Cancel any month
Your benefit
1 month free with a new number, 2 months with your own number
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Zero Waste
€4 a month
Everything you need, nothing you waste.
Choose this plan (Zero Waste)Included:
- 4 GB data
- 400 minutes of calls
- 400 SMS
1 tree planted at activation
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Most popular
Rise
€8 a month
The best balance between price and usage.
Choose this plan (Rise)Included:
- 8 GB data
- 800 minutes of calls
- 800 SMS
1 tree planted at activation
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Boost
€18 a month
For those who want more, without compromise.
Choose this plan (Boost)Included:
- 30 GB data
- Unlimited calls
- 100 SMS
1 tree planted at activation
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Wild
€24 a month
Total freedom, and a new tree every month.
Choose this plan (Wild)Included:
- 40 GB data
- Unlimited calls
- Unlimited SMS
1 tree planted per month
Good to know: keeping your number and an eSIM are free, shipping a physical SIM card costs €5. If you take a new number, you pay one month up front, and we settle that on your first bill. Extra data costs €1 per GB.
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5 out of 5 stars
Happy purchase
From ordering eSIM to get connected took less than 3 hours. I had few questions while ordering and they helped me immediately by the chat. I'm very satisfied with their price and service, and happy to plant a tree!
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5 out of 5 stars
Extremely easy order
Extremely easy order prices and fast delivery. Activation went smoothly too. This was my second SIM. Have been using my first one for over a year now without issues. Contacting customer services is usually fast and efficient.
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5 out of 5 stars
Quick and clear answers
Quick and clear answers.
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5 out of 5 stars
Very friendly lady on the telephone
very friendly lady on the telephone.everything went good and nice
Why UNDO
Three reasons to switch
With every new subscription, we also plant a tree in our own forest in Ibi Village, Congo.
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Orange’s 5G network
You call and surf on Orange’s network, with 5G if your phone supports it.
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One price, from €4
No introductory price that goes up after a year, and no 12- or 24-month contract. Every plan can be cancelled monthly.
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What you don’t use, you keep
What you don’t use in a month rolls over to the next. With Zero Waste and Rise, your data, minutes and texts; with Boost, your data and texts; with Wild, your data.
Real impact
Our projects
For every new subscription, we plant a tree in our own forest in Congo.
Frequently asked questions
You might be wondering…
How and when do I get the discount?
As soon as your number works, email support@undo.be with your own mobile number and that of the person who referred you, within 30 days. The discount comes on your next bill after your email. If you keep your number, the second €4 discount comes on the bill after that. If you use another discount code or promotion when you order, you can’t take part in this offer.
Who is eligible?
Anyone who isn’t an UNDO customer today and hasn’t been in the past twelve months. That can also be your partner or someone you live with. A second number in your own name doesn’t count.
I’m already a customer. How does referring work?
Anyone with an active UNDO plan and no outstanding payments can refer. Make sure the person you refer has your mobile number: they report it to support. If they forget, you can email support@undo.be yourself with both numbers.
The discounts stack, up to €48 per twelve-month period. On Zero Waste that’s a year free. If your discount is larger than your monthly amount, the balance carries over to the next bill. If the person you referred cancels during the first month, or their first bill goes unpaid, we may reverse the discount. If they stay a customer, you keep your discount, even if they cancel later.
Offer terms
The “Pass it on” offer has been running since 15 September 2026, with no end date. UNDO may change or end the offer and will announce this in advance on this page. If you order before the announced end date and let us know within 30 days of activation, you still get the discount. €4 off one monthly bill per referred member, or €4 off two consecutive monthly bills if the number is transferred, up to a maximum of €48 per twelve-month period. Cannot be combined with other promotions. The referral must be reported within 30 days of the new customer’s number becoming active.
General questions
Switching to UNDO
What do I need to order?
Just itsme. You use it to create your account and we verify your identity, without paperwork or copies. If you're keeping your number, also have your customer number and the SIM card number of your current operator at hand.
itsme not working? Check that your itsme app is up to date and try again after 5 minutes. Still not working? Contact itsme. No itsme yet? You can request it through your bank.
How long does switching take?
With an eSIM you're usually active within the hour. A classic SIM card is shipped within 1 working day and usually delivered by courier within 2 working days.
If you keep your number, the transfer usually takes less than 24 hours. That depends on your current operator, who has to release your number. Until then, your old SIM card keeps working.
Can I keep my number?
Yes, and it's free. When you order, you say you want to keep your current number and give the details of your current operator. We handle the transfer.
Enter your customer number and the SIM card number of your old operator exactly. A mistake there is the most common reason a transfer is refused.
Your old SIM card keeps working until the transfer is done. You get a text as soon as your number is active with UNDO.
Your old subscription ends automatically. You don't need to cancel it yourself.
You can follow the status in the app or in My UNDO, under YOUR TARIFF. As long as the box around your number is grey, the transfer is still running. Once it turns green, your number is active.
Does UNDO work with an eSIM or a classic SIM card?
Both. When you order, you choose an eSIM or a classic SIM card. If you choose an eSIM, you enter the brand and model of your smartphone and we check right away whether your device supports eSIM.
An eSIM costs nothing extra, you get it by email and it's usually active within the hour. A classic SIM card is a multi-size SIM card: you push out the right size yourself (standard, micro or nano). Shipping it costs €5.
Why do I pay in advance with a new number?
If you take a new number, you make an advance payment when you order:
the price of one month of your subscription
plus €5 if you have a classic SIM card sent to you
The advance payment is settled on your first invoice.
If you keep your current number, you don’t make an advance payment.
Why is my first invoice higher?
You pay from the day your number became active. Your first invoice, at the start of the next month, therefore has two parts:
the part of the month in which your number became active
the next full month
Example: if your number has been active since 15 September, your invoice at the start of October covers 16 days of September and the whole of October. From your second invoice, you simply pay your monthly amount, plus any extras or usage outside your bundle.
If you took a new number, the advance payment you made when you ordered is settled on this first invoice.
Am I tied to a contract?
No. There's no minimum contract period. You can cancel your subscription every month, and you can always take your number to another operator.
Which plan suits me?
Choose based on how much data you really use. Check your usage over the last few months.
Zero Waste (4 GB, 400 minutes, 400 texts): if you’re mostly on wifi, for a second number or for a child’s first phone.
Rise (8 GB, 800 minutes, 800 texts): if you chat, navigate and listen to music on the go every day.
Boost (30 GB, unlimited calls, 100 texts): if you call a lot and need more data, for example for work on the go.
Wild (40 GB, unlimited calls and texts): if you use a lot of data and often share your connection with your laptop.
Not sure? Start smaller. What you don’t use rolls over a month, extra data costs €1 per GB and you can switch plans every month.
Questions? Our team is here to help.
Send a WhatsApp message, call +32 490 46 19 99 or email support@undo.be.
Weekdays from 8.30 am to 5 pm. Or see all the ways to reach us.
