Debiting my account twice

Since I've joined Virgin active I've never had a problem till now, I didn't pay my membership fee for August for personal reasons and when I was called by the accounts department I made an arrangement to pay that outstanding amount on the 25th, I called the costomer call center on the 26th and was assisted by a nice friendly lady pity I forgot her name, she asked for my details and the payment was made, she even assured me that I can go to the gym now and train because my account is up to date and told me my next debit will go off on the 31st of August I even received an email regarding that, to my surprise on the 29 of August virgin active debited my account and I thought it's for September didn't really pay attention to thought it's just an early debit, till now yesterday my account got debited again now I don't understand what is the second debit for because I made my outstanding payment and they had to debit for this new month, which they did on the 29 what's this second debit for? What's frustrating the most is not having a call center to attend to these matters on weekends but the clubs are opened on weekends