Don't walk, but run to the landlord/tenant board, and tell them your situation. There is no legality in eviction without paperwork from the court for one. If you were withholding rent, did you give a written notice to the landlord, and make a copy for yourself? If you did, make sure that you show it to the board, but it isn't enough that you were withholding the rent, in the letter, you have to tell the reason why you are withholding it.
Also, if you have witness letters to the effect that you did not abandon the apt, this would also help to support you in proving that they were the ones in the wrong. Like I said, RUN to the landlord/tenant board. Hope this helps, good luck.