Cancellation

i sent a cancellation letter to zone fitness and they sent an email confirming that my membership was cancelled after 3 months today i receive a SMS stating that they handed over my account to their attorneys when i call they are telling me that the are fees that i am supposed to pay and they are not aware that my membership was cancelled.someone has to take responsibility of this. i want to know who sent me the email of the confirmation that person should take responsibility because i am not going to pay any fee. i will take this matter further if its not being attended.