i cant download anything anymore

last year I got a $30 visa gift card for Christmas and I bought a song pack on osu stream and the next day I got a message saying "there was a problem with previous billing...." and every time I try to download anything it asks me for my card info and I put the info from the gift card in the boxes and it said it was declined.today i borrowed my mom's card thinking I just have to replace my payment method. when i put the info in the boxes it was also declined. I need help but I cant call apple because i cant afford phone service and if this helps I'm on a iPad 2 (i think) with ios 9.3.5