False adverti*****t

I was called about a month ago to add a package to my existing contract which provides data of 30 gig a month and was told its an extra R11. I agreed and added it as i thought its value for money, then when the day comes i must get my benefits my minutes and everything is gone, called mtn and the consultant said its the 3rd party and they cannot help i must call them to sort this out. WAIT!!!!!!!! Firstly why must i call a 3rd party company whereas i pay mtn, thy must take it up with them. Secondly my bill comes and its now not a extra R11 added its close to R190 extra from what i used to pay. PLEASE SORT THIS OUT MTN!!!!!!!!! I am so disappointed