Unfortunately if you have executed a lease, paid money and accepted the keys you are now liable for the full terms of the lease agreement. Some states do have a “right to rescind” law on the books that you can use to cancel the lease, but usually it is not that simple. You would have to check the landlord-tenant code for your area. Usually it is “http://www.YOURSTATE.gov”
The best thing that you can do is explain your situation to the landlord and let them know that you understand your obligation and you want to resolve this matter and take care of your financial obligation. The obligation of the tenant that quits the lease before the end of the lease term is usually limited to:
1. Paying for the rent for the remainder of the lease term or until a new tenant moves in and pays rent. (At no time can a landlord collect rent from two people on the same apartment under two different lease agreements)
2. The reasonable cost of advertising for a new tenant.
3. The cost for any damage occurred while you had possession of the keys.
4. In some cases, your security deposit may be confiscated-depending on your state code.
It is in your best interest to resolve this situation because it can adversely affect your credit and landlord references which could hinder your ability to get housing in the future. At very least the landlord must give you an itemized accounting of what charges you do own.
If you feel that the landlord is trying to take advantage of you and demanding more than is acceptable under the landlord-tenant code then I recommend that you contact an attorney and take the necessary legal action.
I wish you the best of luck in resolving your situation.