Nokia 6255i / 6256i

I work for a cell phone company and i'm getting tons of complaints about this phone and bluetooth when its been connecting for a day or so after one call the answer key on the headset quits working even with turning the headset off every nite to charge it we've tried 5 or 6 different headsets all having the same problem only thing we've been able to do is turn the bluetooth off on the phone then it works again for a while. Anybody else had this problem?