The business will help plug the hole left by the departure of the pan-European O2 account to the start-up Vallance Carruthers Coleman Priest in January 2002.
It is thought AMV was handed the UK business without having to pitch against its sister roster agency St Luke's because of its experience from working on BT's former mobile arm, Cellnet, now O2.
BT officially unveiled its new mobile service last October but it has received only limited promotion. So far, BT has used its extensive online presence to sign up customers, and the service has also been promoted on BT phone boxes. However, it is now planning an aggressive re-entry into the market.
No-one from AMV or BT was available to comment.