why the credit card declined?

I was using my prepad visa card and i have a few dollors on it. but when i redo the credit card info, it still declined for a few times. Most of the apps are free but still it needs to have the credit card details. why is that? I am planning to remove the credit card off the setting as soon i top up the money.

is there any other ways to avoid that or is there are special system that i can pay them for next round of payments?