How do I get my Apple Pay back

It appears that you came to the Community from an article about Apple Cash restrictions. Is that the problem you are experiencing with Apple Pay? Please explain your problem a little clearer. Here is some guidance on how to get the most out of Apple Support Communities→Writing an effective Apple Support Communities post

Sending money is done via Apple Cash. You must have money in that account to send. Follow the troubleshooting steps in that related article, or see this. If you can't send or receive money with Apple Cash - Apple Support

Apple Pay and Apple Cash are 2 different things. You cannot sends money or receive money over Apple Pay.

You send and receive money through Messages, and it uses Apple Cash to store the received money or to get funds to send money to someone else.