I didn’t left any games but it said that I left a game so that they give me a punishment witch is that i have got to pley with others who left a game. it’s nonsense!
This might happen if your internet connection drops out frequently at bad times, such as the match ending. To get a punishment that also might mean it happens fairly frequently as I think there is a little forgiveness if it happens very rarely.
The solution, as always, is to either play QM or ARAM games. ARAM is the usual spot for it as the matches can be shorter than regular QM and with skill you might achieve >50% win rate due to the lack of match making in that mode.