Discovery taking money that isn't theirs

I finally received post in Feb and saw a few Discovery letters all showing the same thing that I owe them R106.40 and I must pay this amount within 30 Days of receiving this letter. I then called Discovery and spoke to a consultant and they said that the pharmacy messed up and its not my fault, but I must still pay and don't worry you don't owe anything, cause it was taken from an amount that was due to me of R500 from our fitness assessments. No notification or details of what this is or for or why this has happen have ever been sent to me. I have specified my main method of notification is Email, yet I have still never received anything from them. The consultant then laughs at me, I then ask to speak to a manager. Cause its not my fault but I must pay for it. And to top it off the payment to me was for R500, not showing less the amount of R106.40, and due to it being so late I cant even fix this issue which it could have been if done in September 2014. I am now on the verge of cancelling Discovery cause we pay and pay and battle to get assistance when needed. The details of the consultant are Nomase *** and Manager Anele ***. Lets see how long this takes