cheater

It is against chess.com tos to discuss cheating in the public forums, so please keep all discussions around cheating in this club where it is allowed https://www.chess.com/club/cheating-forum
How to report someone on chess.com https://support.chess.com/article/209-how-do-i-report-someone https://www.chess.com/forum/view/general/how-to-contact-support-1
If the time increased after a move, then it sounds like you chose an increment time control without realizing it:
https://www.chess.com/terms/chess-time-controls