Unhappy member

I've had just about enough of zone fitness, my contract ended in june this year and i am now gyming on a month to month basis, so the decide to increase my monthly payment without consent, the first time i enquired the told me that the additional charges was because of a late payment and this month the same thing, i blocked them at the bank and now I'm paying cash, sent proof of payment and now my membership is blocked saying that i have an outstanding amount because my membership apparently increased. I enquired again and has never heard of them since