Need phone replaced!

On the 28th of December 2015 my Microsoft Lumia 535 phone was taken on a contract. 8 days later the phone was not switching on at all. After charging the phone it still did not switch on. It was taken back to Cell C City View the same day. They sent it for repairs, they then sent the phone back 2 weeks later, the phone switched on in the store but the consultant said we need to charge it as the battery was dead, after getting home and putting the phone on charge it still did not switch on. It was then taken back the next day to the store and they said they would send it back to head office and send them an email regarding the faulty phone. We made it clear to the consultant that we want a new phone as it has been problematic since the start. After numerous calls to the store I get a response saying that they cannot replace the phone due to corrosion! This phone was 8 days old, it was barely used. I will not accept this response from cell c, as this looks like a factory fault! I want the phone replaced with a different model! I am not willing to pay for a phone that is not working for 2 years! I will not let this rest until the phone is replaced!