Hairline cracks along side of USB connector iPhone 3G

After 17 months of constant connecting and disconnecting of the USB cable my 3G has developed cracks on either side of the connector along the back plate. The crack caused a piece to come off around one speaker grille. Now Im trying to find a shop to do the repair since APPLE does not repair the units. AT&T is willing to upgrade me but Im not sure Im ready to add 2 more yrs to my 4 four lines. Their service is not the best in the clearwater, fl area. Many calls get dropped.
Mac Pro Mac OS X (10.5.6) RAM 7 Gigs