Bad service

I Bought a cell phone and it stopped working within 10 days. I took it back and was told it will be returned to the manufacturer and fixed or replaced within reasonable time (4 - 6 weeks). its been over three months and every time I call to enquire I get rude remarks, I said to one lady that if the phone isn't returned I'm not going pay my instalment this month as I'm paying for goods that I don't have and she said to me she doesn't care what I do its my name that will be blacklisted