Disappointed and angry mtn customer

I am so disappointed and disgusted at MTN. I took a contract in March for a 40gig daytime and 40gig night time data. The first month they overcharged me with R2200 in April they charged me R539. I realized that they have been giving me 20 gig daytime and 20 gig nighttime data for R539 whereas I should be getting 40 gig day and 40 gig night. I feel like they robbing customers. I tried to take it up with the salesman but up until this day my query has not yet been resolved. I am so angry. 20 gig data for R539 mtn? Are you serious? I think I'll be taking this up with my lawyers as I am not getting any help. The consultant I called today told me that I should take a picture of the contract and send to him, I mean ***!!! I am fed up, before I cancel this contract mtn would've learned a lesson I swear!!! I regret why I didn't take vodacom contract!!