Unfair ban

Last week I was permanently suspended, the reason was illegal software use, which I never used, my account is 5 years old, I started when renekton came out. I asked riot support to clarify my situation, they only replied that it was evident my lack of which I was never warned, I could not defend myself and they never showed me evidence. I am very indignant since I never committed any fault, I am not even toxic, i never troll, I really follow the code of the summoner. I think this in very unfair, how can i know that this is not a riot system error or something like that. Im angry and sad. Now im afraid if i start a new account i could get ban at anymoment without reason or evidence.