The process if an umpire's radio develops a fault is as follows
Go to http://www.umpiretalk.com/returns.html (see link below) and follow the instructions. There may be an amount of £25 payable by the umpire, but if the issue is found to be a manufacturing fault with the radio, this will be refunded.
There appears to be a common complaint that the Jabra headsets lose connection during a game and either all communication is lost, or communication only works in one direction. This may be an issue with the compatibility between the Jabra 2.5mm plug and the socket on the radio, or may be a faulty Jabra. In both cases the supplied boom headset and microphone will usually work.