Dicovery mistake cost me money!

We decided to add my husband as a dependant on my existing plan effective January 2015. We started this process in November 2014 to make sure we give Discovery sufficient time for changes to be made. I however was given and confirmed the incorrect monthly instalment more than once telephonically. I was told that my monthly instalment will change from R1976 to R3532 when adding my husband to my Classic Saver Plan. This was also confirmed with the consultant over the phone. I was however debited R3882 on the 3rd of February 2015. NOT the amount agreed. I once again contacted Discovery (*** to call made on 03.02.15) stating that I'm not happy and wanting an explanation as to why there was more deducted from my account than quoted? The consultant contacted me back at 11:43am today (04.02.15) stating that he has listened to the phone records and that they indeed made a mistake as Discovery had the incorrect information at the time. I would think that the difference of R350 a month (total R4200 per year) is a big mistake on their part and I will not pay for it!