Beware of mobile plus

Last week Friday I received a phone call from Mobile Plus (saying they are MTN) where they offered me 15GB FREE data due to the issues I have been experiencing with my 2GB on my contract. These people had access to all my private information including my ID number and my monthly debit order amount. The person on the phone kept on saying it was at no extra cost and then continued to mumble t's and c's and again assured me I will be getting free courtesy data at NO EXTRA COST. I then ended up going to MTN to see what was going on because I was suspicious of the call. I then found out my contract had been migrated to a Gold package which I cannot afford. The man that assisted me said there was nothing he could do and that I should call Mobile Plus. I have phoned them numerous times to reverse the process but was told I would pay a pro-rata fee for downgrading when I didn't even give permission to have it migrated in the first place. I am totally disgusted in the disregard Mobile plus has for people. They are complete **** artists