Bad service at Parow mtn Cape town

mtn gave me the wrong contract from march 2020 up date, my cotract that i signed for was 20 gigs day and night. when i go to parow mtn Cape town where i opend my upgrade the said the will fix it untill to today nothing have been done about the this , i stll recieving 15 gigs day and night insteady 20gigs.The lady that was helping me was Kim.when asked kim the lady that helped me with my upgrade she said , the head offoce the the codes that their wre the promo book were wrong how come they can advertise something that is wrong that is my quetion, i think someone is lying here. i am still waiting for responce even today.

Please i need help.