billed wrongfully & without being informed

I had a contract with Virgin Active and my monthly fee was R84 (Discovery Vitality). I was billed R84 on the 09-12-2015 for decembers payment. I was then billed R113.75 again on the 31-12-2015 for january 2016. I called V.A to find out about the fee increased and was told it was because i had not gone to gym 36 times within a 12month period. However, i was then billed R227.50 for february 2016 and was told it was also because i had not gone to gym 36 times within a 12month period. How could my fee have doubled twice just for not going to gym 36 times within a one 12month period from january 2015 to end of january 2016? I was told i would be called back and I never was. Also these amounts were just subtracted from my account without any sort of warning or being informed or reasoning