Help me

I had a free trial until December 6th. When I tried to cancel, it wouldn't let me, and now it's about to charge me over €100 without my consent. For now, the only thing saving me is the lack of funds on the card, but right now I can't top it up, otherwise I'll be charged money I didn't intend to spend. Every time I try to cancel, there's an endless wait that leads to nothing. By the way, I was promised an email the day before the end of the free trial which was NOT sent to me. Please help me