Make a support ticket. Dont submit it multiple times, but if you talk to them and close the ticket, make another one. Keep making them. Recently someone was banned for the same thing and it took her several talks with support to get it reversed. They will say they cant share details and that they know it wasnt a mistake. Just keep hounding them till you get the right person.
However, since you havent logged on in so long, your account was probably hacked. Since we are all responsible for the security of our accounts, I wouldnt get your hopes up. I think they have a way of recovering the account, but its not guaranteed. Prepare for a lot of questions about first champion purchased, date the account was made, other random things like that.