Pay even though the membership was cancelled

Started a new job this year which required me to move on to my own medical aid which meant my dad needed to remove me as a dependent on his. Having done this, he also called virgin active to cancel my membership because he was aware that i would need to rejoin with my own vitality. The *********** operator failed to do this and not aware of this I kept going to gym. Now when I'm supposed to rejoin and pay the vitality once off fee, I'm refused because I owe virgin active for their incompetence. It is now my fault that I went to gym because someone didn't do their job and I have to pay for the mistake, not once but twice. I have been at Virgin active for 11 years and the service is pathetic!