I feel like I've been ****med

I bought a phone last month on the 13th, in 3 days i noticed that people can't hear me, i took it back, they tested it and confirmed that it was faulty they sent me back told me to cone back following day manager was not around ,i went back following day, they booked it back to MTN and remember on the contract they say if its less than 7days they give you another phone if its not my fault, even today i haven't received it, they once called and said they couldn't access it cause of password,i gave them that was last month, even today no one ever called and i already started to pay for the phone that i don't have,am very angry right now.n Truworth Alex mall in Johannesburg