BB Curve :: Micro USB Port Damage?

I bought a Blackberry Curve 8520 6 months ago, which is under a year-long warranty, from Carphone Warehouse. A month ago, the Blackberry stopped being able to charge so I took it into the shop and the phone was inspected, and I was informed the phone would be fixed under the manufacturers warranty and returned within 2 weeks. Exactly 2 weeks later I was told to collect my phone as it was fixed and it had been returned UNFIXED as I was told the damage was NOT covered by the warranty, after being initially informed it was. What has happened is one of the prong inside the micro USB port has broken off so the phone won't charge. This has also happened to a friend of mine, so surely it is down to faulty materials? I don't understand why this is not covered by the warranty.

I was wondering if Blackberry themselves would be able to fix my phone (as Carphone Warehouse are refusing to, unless i pay £170 - more than the phone is worth. I have taken this up further with them but have constantly received poor customer service and am not willing to deal with them anymore).