usb connector?

First off,  I love this phone.  I've had it since March now,  and the only major issue I've had with it is the unreliability of the mini usb connection.  I have 3 different chargers for the phone,  only one of them works reliably.  The one that came with the phone <i.e. the one that you use to sync with the PC>  rarely works at all.  I can both plug it in to the wall using this cord,  and the computer,  but the connection is sketchy at best.  When plugged into the computer,  I can watch the screen of the phone and the pc and see the connection going on and off.  The biggest reason this is a problem is because the phone does NOT charge reliably.  Does anyone have any ideas on how to fix this problem? Or do I just need to send the phone in for a replacement.