App Store not working; Can't reset restriction passcode

Earlier today my mother tried to download a free game to her iPhone, it said she needed to verify her credit card information, she did, it said it was declined. She checked her bank account and everything was normal. She went back and tried it again, it still didn't work. She tried on my credit card and it still didn't work. I thought it might be the fact that her iPhone hasn't been updated in a while so I went on to do that and it is protected by a passcode and she doesn't remember what it is. I have tried numerous things including her unlock code, a few previous unlock codes, my birthday, the birthdays of my siblings, and her birthday: nothing works. She currently has iOS 8.3 and her carrier is Verizon. Any ideas on how to fix these two problems would be greatly appreciated. Thanks in advance.