My account got hacked and banned

Hello, my username is Avern, my playerID is 47845 and Ally Code = 375-732-811. I joined swgoh in 2017 but stopped playing then started again in 2019. I have been playing honestly for 3 years. But this year, A month ago something bad happend. I was in the last semester of my college, besides that I was looking for a job and preparing for GATE exam. I had enormous study pressure. So I told my cousin brother who also is a swgoh player to use my account and complete the progress for Jedi Master Luke Skywalker. I sometimes opened the game just to view the progress and nothing else. He unlocked JML and started journey guide for SEE. Now a month ago(6/7 th April) I opened the swgoh and found that my accound has been banned for repeated offense. I could not belive my eyes. I thought someone has reported wrongly. So, I googled about it and came here, complained and I searched the discussion. After that I went to my swgoh.gg account and searched for grand arena history and found some battle history which could only be explained by some kind of cheating. So I asked my brother if he had done something but he denied telling he has not played GA for a time and did not open regularly. Then remembered that some months ago(2-3) my insta account was hacked, an hacking attempt on my steam account was also made. The facebook account which was linked to my insta and swgoh account, was hacked also. As far I have seen my brother playing, he is a fair player, so I dont think he cheated, But I am sure my account was hacked. Now my college is over, I want my account back. I am being punished for something I didn't do. Last year I invested a lot of money(2000-3000 inr) after my account. Please help me.