Very angry new client

OMG!I'm a new client to mtn and I think it's a biggest mistake I have made,took out a black friday contract with them in nov 2020 and received the router in dec 2020 only to find I only got 400 megs of data from a 100 gigs of anytime data,then I called they saying something like cut off date and data will come through on the 12 jan 2021 so I left it and wait till today,and still I got 500megs of data I called and after sitting on the line I got told system problems and can I please call in 24hrs.so then i email and got some answers, that my contract is 500 meg data that I neva took out,I sent a screen shot of the contract I took and still I'm not getting answers,I'm fuming and very angry if this cant be sorted I need to cancel.