BT SNERGY,IS THERE ANYBODY WHO REPAIRS THESE PHONES?

BT SYNERGY MOBILE WORKSHOP PHONE,JUST OVER A YEAR OLD AND IT WONT HOLD ITS CALL IN IT JUST GOES OF AND ON IVE CHANGED THE BATTERIES BUT NO LUCK,BT CANT OR WONT REPAIR IT SO I WOULD LIKE TO KNOW IF THERE IS A COMPANY WHO COULD REPAIR IT,VERY POOR SERVICE FROM BT,SELL A PRODUCT THEN WANT NO MORE TOP DO WITH IT