Gym Company Pinetown, How hard can it be to cancel a Membership???

I signed cancelation forms in September and agreed to pay for the 3 months notice required,but every month they're still trying to debit off my account. I have called countless times to query about this, it's either they say they cannot see my forms or others tell me that they'll remove me from their system...how hard can it be to cancel. Gym company is bunch of *****sters!