EVERY MONTH IM BILLED INCORRECTLY - THE ACCOUNTS DEPARTMENT ALREADY KNOW ME BY NAME

Since the day I started with this contract at Virgin Active its been a nightmare! every month I have to call the accounts department because they billed me incorrectly THEN I HAVE TO WAIT TO GET MY REFUND BACK !!! - I WOULD LIKE TO KNOW IF I CAN START CHARGING YOU INTEREST FOR HOLDING ONTO MYYYY MONEY ???? How are you getting this wrong every single month!!!! - Now Virgin Active offers me a 3 month discounted membership for not cancelling after my contract has finally finished AND THE ACCOUNTS DEPARTMENT STILL BILLS ME WRONG !!! - Never had problems like this when I was a member at Zone Fitness - so much for Leveling up