Unwarranted Billing

I recently canceled my subscription and as per agreement I was to be billed on the 28th of the month for the cancellation fee. Now planet fitness keeps deducting money from my account and every time I bring this up no one knows what to do. It's unfair to have money deducted unreasonably from your account on 2 separate days in one month!!! It's actually *****ing from a person under the guise of a service fee!!!