Can an Army Reserve contract be cancelled before ETS and reporting to unit?

The Army could offer an early out program but you as the Soldier can't go in and say "Ya, I'm done" and walk out. Now if there's a breach of contract that's different. However, the way I read your question and your post underneath leave me a bit confused.

did you sign the contract?

SPC (Join to see) Just because you have not reported to your unit there is a lot more in the works behind the scenes. My guess is going to be no to your question. What does your orders say. Does it have you reporting to the reserve unit or the IRR? My guess is the new unit. Also your DD214 is going to say command to which transferred is the gaining unit that you choose. The person that you really need to be working all this through the Reserve Components Career Counselor (RCCC) that you signed your reserve contract with. I hope that this helps.