Frustrated with the cancellation process

I cancelled my contract with Planet Fitness in October and had to follow up with them on several occasions. Four months later, and they have continued to debit my account, without any confirmation of the contract being cancelled. Currently they have debited about R2000 after the notice period. I have been to the gym about 4 times over the past few months to speak to the consultants and manager, however they are constantly delaying the process and giving me excuses about a systems delay. I have also called on several occasions and followed up on Whatsapp. WHY DO I NEED TO CONSTANTLY ASK THEM TO REFUND WHAT WAS NOT THEIR OWN TO TAKE????? Extremely frustrated.