Lease Cancellation Agreements

[Mariad]

Has anyone ever had to sign a lease cancellation agreement instead of a short term lease? When it was time for me to renew my lease I told my LL that I need a short term lease since I would be moving. Instead I was told that I had to sign simultaneously a one year lease and a lease cancellation agreement. When I moved out I used my security deposit toward my last month's rent and now they are using that against me to claim that I was in default by doing that and that lease cancellation agreement is null and void and I am responsible for the six months left on the lease! I acted in good faith when I asked for a short term lease and since I had no other option I signed what they wanted me to. I now feel like I was tricked in to signing a one year lease so they can do what they are doing. If I had signed a short term lease and lived off my security for the last month I would have been only responsible for any damages. Has anyone else had this problem?
THanks