voyager focus uc stopping sound and run it over and over again

Hi, I have a Plantronics voyager focus uc hedset and wihout mic it working fine but when I join to call/start using microphone hedset stop sound for half sec and start it for half sec over and over again. On others computers same problem. Earlier I can connect it to laptop via micro USB cable and headphones and mic work good but now even that doesn't help. My question is: what i should to fix it.   I don't know  where put this subject