Refused to attend to a query as outlined in theirc

I upgraded my mtn contract at menlyn on the 23rd October 2015. The sales person inserted the simcard and switched the phone on. I saw the phone and I put it in the box. We signed papers and I left. Later I noticed that the phone was on safe mode always. Switched it off and still it remained on safe mode. On Monday the 26th I took the phone back to the shop. Showed it to them. The consultant consulted with the manager (jeniffer) in private and then claimed that I dropped the phone and therefore they cannot replace it. They offered to take the phone on and send it for assessment and then I will get feedback either on Friday or next Monday. I found this unacceptable. They then said I can take the phone in myself. They gave me the name and address where to go. I arrived at the repair centre on the 28th. They informed me that they only assess phones after the expiry of the 7 day rule. They phoned the dealer a day she refused to barge. All along claiming that I damaged the phone by dropping it. However the main problem being the volume button which get stuck when pressed. I need your assistance as they have the worst attitude I know of any service provider.