Problem solved! When entering the credit card and billing information on the AutoPay setup page, I omitted the apartment number and just entered the street number. Then it worked! It's all set up now.
I can't even "register" my credit card... The bank said that they received a call from another person who was having the same issue with Public Mobile. So, something is not working right with PM site. Hope it will be fixed soon.
I'm in exactly the same situation. I got the same message and phone the bank. They said everything is good on our end (bank and me). I guess I will try later again...
