What to do when your support grief?

So I was playing an offlane, then my support use his spells to get all the cs, I didnt know what to do so I feeded down mid, and ended up I got banned lol, so I think what I did is what I shouldn't have done so I'm asking here. What would you do when your support intentionally gets the cs instead of you? Should I sell the early offlane items and switch to play 4? But I use my queue point for the role I selected right? I'm so confused lol. Also can we have an appeal feature after getting issued an overwatch so we can explain ourselves too? asking for a friend xD

PS. I played Tusk when it came to def hg I snowballed that griefer to the enemy team every time he respawned

Edit: Abandon doesn't get you banned right? So how does it work again? Will 2 abandons in 10 games be a penalty? or 20 games I couldn't remember

Edit2: I did queue after this game and the same guy ended up in the enemy team he picked luna support and kept stealing his offlaner cs as well, in the end, I won, and the enemy team typed "report luna"

When he's in my team: 6948523817: lion
When he's in the enemy team: 6948553259: luna