Overdeduction by Telkom

I took a contract with telkom through Mondeo sometime in April. The contract contained a sim only deal of R70 and a Wifi-Router for 170. In total, I was supposed to pay R240. However, I am paying R270. I went to the telkom shop at Park station to fix that. They told me to never take deals from such agents like Mondeo because of such mistakes and that the R30 difference wont be defunded. I was not happy with that but at least I had hope that they will now deduct R240. Unfortunately, till today they still deduct R270. I am really disappointed, too disappointed to even go back to the shop again because I wont be refunded anyway.

I then wonder why they would work with such agents like Mondeo if they dont trust them like the consultant at Park station said.