it used to be eServe... but they had dropped being the service center for UE/Logitech. Logitech has been very very slow in replacing faulty earphones (I had to wait ~2 months for a replacement pair!)... and eventually a lot of people complain about the slow RMA process.
Seriously, don't be bothered to repair your faulty UE phones... I strongly recommend you get other non-UE phones. If you favor UE sound signature, you might wanna try our Shure or Westone.