Can't top up prepaid phone, I only have a credit card

First of all, sorry for raising the question in English.

I have a prepaid KPN SIM which I have been using for a couple of years now.

I am struggling to top up so I can keep using the number. The app won’t load the payments page, so I tried https://www.kpn.com/prepaid/opwaarderen.

On the opwaarderen webpage, I try to pay by credit card but it says “U kunt geen gebruik maken van eenvoudig betalen omdat de limiet bereikt is. U kunt nog wel betalen via iDEAL”.

I have tried all sorts of amounts but the webpage keeps raising the same problem.

Unfortunately I do not have iDEAL or a Paypal account and I rely on the credit card functionality.

Would you be able to advise?

Thanks