How do I update my apps? I have a problem where whenever I try it says “verification required”

I bought something on a game that came to around 15$ and now it says verification required every time I try to download free apps or update them. I have tried transferring up to 30$ and entering my card, but it says payment declined. I have contacted both Apple and PayPal (as I bought with) and both of them say that their is no problem on their end.