Open Question: Got my xbox360 back from repair and played it for a day because it bro

[Knowledge Bot]

ring of death, E71 and E79 errors. I sent it back to xbox but they sent me it back saying I had tampered with it, I assured them this was not the case but all I got from them was. 'there is nothing we can do'. I don't know what to do as I am pissed. Any suggestions as I have no idea how to tamper with it?