Hopefully they'll do a better job with your phone. Mine went there as well for FFC dust and creaking/clicking issue.
They ignored the dust issue, flashed the ROM and replaced the chassis with another one with the same/more faults including a slightly chipped off SIM card keyhole and a small 'bump' on the chassis where it meets the screen on the top/left hand side.
The best part was when they claimed to have replaced the phone with a new one as they had decided it couldn't be repaired...!
What did you do after that?