How to get unbanned from dragon city?
I used a hack once,3 or 4 years ago
now i'm back to the game and i found my self banned..
I hope there's something i can do to get unbanned....

I doubt it but the only way is to ask SP....otherwise I am afraid you are banned for as long as they have. Note to self: avoid using hacks and cheats, it catches up with you eventually.

Try contacting socialpoint support by email.

Edit: promoting hacks are not permitted, question removed.