Do I have to get a new simcard when changing my prepaid to subscription?

Hi ​@Erineo 

Welcome to the KPN community.

You currently have a prepaid subscription with KPN, but would like to
revert to the Unlimited 50 subscription.

That's no problem at all, of course, and you can arrange it yourself via the KPN website.

Order a SIM-only subscription on the KPN website, and choose the Unlimited 50 subscription in your case.
To port your number, indicate that you have a prepaid subscription and then enter your KPN prepaid mobile phone number. You will then receive a verification text message, which you then enter on the online order form.
Next, enter all your personal information, ID, and bank details and complete your order.
You will indeed receive a new physical SIM card, but you can also opt for an eSIM if your device supports it.
This is because a subscription works with a different type of SIM card, which also allows you to access the 5G network, among other things. If you choose a physical SIM card, you'll receive it at home within 2 to 3 business days.

If you prefer personal contact and assistance, you can visit a KPN store near you, where a representative will help you transfer your prepaid card to a KPN subscription.
Please bring your valid ID and debit card to the store, as the representative will need them to sign up for a subscription.