Hi @Hendrik147, welcome! The quickest way is to call us at 0800-0402 (free). Alternatively we can assist your here. In that case, fill in your forum profile with the telephone and sim card numbers (both can go in the ‘klantnummer mobiel’ field) and reply here when you've done so. We'll get back to you then tomorrow morning. 

Thank you, @Erik_ .
I have entered the numbers in my profile.

Thanks @Hendrik147!

When I check your balance, I see you have a call credit of €0,00, which explains why you're not able to make any calls. If you top up your balance, you should be able to use your card again 

Thanks, @Maja_