Unfixed Dodgee Phone, Poor Service

I bought a brand new phone at the store in springs cash crusaders, within 3 months the phone gave me problems of over-heating and showing colourful lines on the screen so i returned it to the store for repairs because it has a 1 year warranty. 'til now i haven't received my phone and its been more than 4 weeks not having my phone back. They always tell me stories about my phone as if they don't wanna fix it. (1) They always say next week after next. (2) They said my phone was fixed bt the delivery guy forgot to bring repairs for springs and will bring my phone next week and that was said last week. (3) They called again saying it was a physical damage so they need R850.00 to fix my phone after mentioning that it was fixed and i said i wont comply with that 'cos its a lame excuse that its a physical damage and already said its fixed. (4) They called again to mention that they are sorry they will fix my phone at no cost but they WILL order parts for the phone and will take another 6-7 weeks for the parts to be send to them, so in the mean time they wanna give back my phone unfixed after 4 weeks at their store. All i'm asking is my phone being Repaired, Replaced or Refunded.