What were the exact dates for the lease? Is there an auto-renew clause in the lease?
Once the terms of the lease have been ful-filled, you are under NO obligation to continue to pay rent or utilities on a rental unit. That is provided you followed the proper procedures on notifying the LL of your intent to vacate...
Tell the LL to pound sand, as there is NO state law that requires a tenant to continue paying rent or utilities once notification has been givenm, and you no longer reside in the rental unit...