Terrible Service

I have cancelled my membership with this gym but they keep deducting money from my account without my consent. I was on a month to month basis with them before cancelling with no contract in place. Now after canceling they are telling me that I owe them money even though I was on month to month basis with them. I stopped training with them before canceling my contract. I have never signed a debit mandate form with them but they keep of deducting my account. This people are ******.