Problem with Bluetooth reception and disconnecting

My iPhone 5S running Version 9.3.1 is experiencing some audio interference when using my Plantronics PLT Legend Bluetooth ear piece. I can be having a normal conversation with the ear piece and then I start hearing a garbled noise and the Bluetooth connection drops. The other party also says that I was breaking up before the disconnection. I have two of the ear pieces and both are experiencing the same problem and both are fully charged. I think this started happening with the iOS 9.x.x updates. I have already "forget the device" and then repaired it. Any suggestions are appreciated.