Summons after cancelation

After 2 years of having the same issue with my bank account number where I had to call to correct it, Flexi Club has still managed to get it incorrect. I then had to wait 3 months for feedback for wanting to cancel, within this time I have been blacklisted due to their mistake. I have sent numerous mails trying to find out what is happening with no response. I have now received a summons from Flexi to an outstanding amount when I was promised telephonically there will be no outstanding balance once cancelled. I then called on Monday to find out the reason, I was then told that my membership has not been cancelled. I then spoke to the person dealing with and was promised a call back the same day, I sent an email for a follow up. it is now Thursday and I still haven't received a response