First of all i am not a new user at Binance and neither i mark the payment as completed without paying the amount. So you don't need to assume things that did not happen.
Usually if one party tries to cheat, binance will take the proof from other party and resolve the dispute. For example, if he has not released the money, the bitcoin or USDT in escrow would not have released so there is no point cheating in binance P2P.
1. Reporting the account to the customer support
2. Opening a dispute
Reporting the account to the customer support does not automatically lead to opening of a dispute, and they even warn before one makes a report, that, if they maliciously do it, they could face the consequences. I don't think the warning is a result of someone or group of people reporting the OP's account, though.
Yes i contacted the support and they told me that there was one order in the past when the buyer had sent me more money and i need to return it. I told them that I already had returned the money. They confirmed from the buyer that the issue was resolved and now I can do the P2P trading without any issues. I guess someone bumped this old thread, anyways thanks for your advice.