Billed for someone else's account!!!!!!

Over the past year I have had Debit Orders go off my account from Planet Fitness even though I DON'T EVEN HAVE A PLANET FITNESS ACCOUNT ANYMORE! I don't owe them money and haven't been there in years. My account gets debited EVERY month by them and EVERY month I need to reverse the payments as I don't have an account with them. There is someone at the gym who went to school with me that has a very similar ID nr to mine as our birthdays and birth years are exactly the same. I have phoned Planet Fitness in Roodepoort 6 times already and it just doesn't get fixed! Now my credit record at FNB is affected as they say that a reversal on my account looks like I am not paying my accounts!!! I am livid and have incurred bank costs every time this happens. I would like my money back and all the bank costs I have been charged by FNB. Not to mention how this has now affected my credit record too!!!!!! I am sick of bad service esp by Planet Fitness as I have spoken to so many people there explaining the situation! SORT THIS OUT!!!!!