Physical damage excuse

I bought a Blackberry 9720 from Game Pavilion 9 months ago. At first the ear piece became faulty so I used the earphones instead. A little while later the earphones also stopped working and the housing came loose. The charging pin also moved out of place. They insisted that I had dropped the phone but I said that the housing is loose because the ***** came loose, which we discovered in the shop. It went in for assessment and they said its been taken out of warranty, and the repairs will be more than the value of the phone. At first they said that if its a common fault it will be repaired within warranty. I've been quoted between R250 and R300 by two independent repair outlets and they said that mine is a common fault and they deal with it daily. Its a poor quality phone and the charging pin has no support besides the solder, and the housing is fragile with plastic threads for *****s. There's a 2 year warranty but of no use to me. The agent 'sneaked' in a comment that there was a scratch at the back and a crack on the side. Well the housing came loose which created weak spots, which is common sense. They agreed to send my phone back to a closest branch but now they say they don't