Nothing suspicious about the rating rise since chess.com uses the gliko rating system.
How do you complain about a possible chess cheat?

Well unless this opponent is a chessmaster in the making I cannot understand why he/she is easily beating all other current games of 1500+ opponents. I have checked their present games
Hi, I am currently playing against somebody who has a rating of 1636, has only played 3 games and their last victory was against somebody with a rating of around 1550? maybe I am just being paranoid but I have never started a game with somebody of 1300, and now they are 1636. I don't deny I have played pathetically during this game but the rating is suspicious