Max level boost

I purchased path of firf and Use max level boost by Character lv 80 by mistakenly Continue with the support center did not respond What a solution to recover

Did you click through all the "are you sure" prompts and make it permanent? If not, you can simply undo the boost(1). And no, the support centre does not respond immediately. While waiting, play on a different character for a while so that you aren't benefiting from the fact that you've used the boost. (Making use of the boosted state of the character will make CS less likely to help you, which is quite reasonable if you think about it.)

(1) Click the booster diamond in your shared inventory slot and pick "Undo boost" from the pop-up panel.

Customer support is definitely the way to go.

That said, I wouldn't worry to much about this. Leveling in this game is very fast from 1-80 and should be done on the first character any way to get used to and get to know the game.

In case customer support can't help, simply bench the level 80 for later and start a new character. It's fine and you'll get enough fun from leveling one naturally the first time.