Unhappy customer, very disppointed with MTN cell number ***

I'm very disappointed with MTN, i saw an advert in June 2019, the advert said you get a sim only contract 1GB for R99, then you can add a Samsung A20 with the same contract were you will pay an extra R80, on the 29/06/2019 i went to MTN store in Greenstone i even gave them a pamphlet of the contract that i wanted i was assisted by Andile, then i took insurance in think for R89+, upon receiving the phone i had 50+GB, 50 MTN minutes and 60 sms, i called MTN today because i had a balance of 515.07 MB but to my surprise i was unable to surf the internet i can only send and receive WhatsApp messages, one of the MTN champions told me that apparently i receive 50 MTN minutes, 60 sms and 350 MB, but that is not the contract that i wanted, i wanted a contract were i was suppose to received 1GB, not 350MB, and the reason I'm calling now is because MTN gave me 50GB on board after i signed the contract which expired on the 28.07.2019. One of the MTN champion that i spoke to today the 07.08.2019 did not even assist me with my query instead she gave me a number *** to call and in order for me to call that number i have to but airtime, can someone from MTN please call me and explain why the terms and conditions of my contract has suddenly changed.