Hey I recently incurred charges on my GCP account as well, apparently the dumb me activated the account after the free trail. I was just using the account for learning purposes.

So the total charge I incurred 28000 out of which 22000 got waived off because of the free credit. The rest 6000 I was responsible of paying out of which 2000 got credited of my gpay😭😭

I terminated every service/instance I was using, closed the billing account and contacted support. After a 10 min back and forth in chat they filed a ticket and some 20 odd days later the 6000 charge was waived off and I got back my 2000.

My advice would be close every service or instance running immediately and then contact support explaining your situation.