Default listed on my credit report and have never signed membership !!

Gym company is the biggest con artists ever ,I once tried to join the gym and was advised to complete a form with my banking details and I will recieve a yellow form as proof of l membership.I gave sales consultant my banking details and never seen or heard of him again I was never given a yellow form and could never ever gain access into the gym .I consulted with accounts lady precious who advised she will rectify the issue but she never did I continued to get debited but never recieved proof of membership and could never gain access into the gym ,I'm so frustrated now as it is one year later that has passed and I find out that I have a bad default by them on my credit report with no communications or emails or even a simple call to advise me I had no knowledge of this until my credit report was sent to me .If i get no call regarding this issue my lawyer will handle this matter further .GYM company has violated my every right and I demand an explanation .I have never given gym company my I'd number so how did they list me knowing that I have not signed any membership agreementonly given my bank details . My credit report was good until they did this extremely upset!!!