Charged a Different Acc to whats on Application for 2 Years and holding me liable ?

I signed up at planet fitness and went a few times as most people do. It was a short spell before moved away for abit and then back home again . Because I hadn't been going it wasnt top of mind and I never saw a debit order even attempt go off . So I carried on with life. A year later debt collectors are hassling me for a years worth of fees, as this made no sense I simply asked for the contract, for another year I have waited for the contract still not received . After 6 months of debt collectors asking for money I settled in order to lay this debacle to rest . Loan behold Planet fitness phones asking for the last 4 months payments , whilst on the call I managed to piece together that these clowns have been charging the wrong bank account for 2 years. They were never charging the bank account I provided the details for . I explained this to the call centre agent who called me a week later asking why I wanted a copy of my contract ( still not received ) .The helpful lady escalated the situation to the manager with my request that we both compromise acknowledging parties at fault . He/She who simply sent a response via the agent saying "No" .

No explanation , no apology for the admin fault . Disgusting