Apple ID & iTunes

Hello, I am currently using iPhone 6s & 5s as well with the latest ios of course.

So the problem is, few months ago I plugged in my 6s to my laptop & accidentally synced my iPhone to the old one that I no longer use with a different ID. And replaced everything back to my old contents. I thought it was alright until I cant use my credit card to purchase anything or download anything at all. I cant even purchase anything for the games. I tried using my other cards but they are all declined.

Worst of all, everything Ive purchased previously was all gone too, including all my subscriptions on iTunes as well.

What should I do?