The move marks the first time that BT has appointed an agency to specialise in business to business. Previously, the load was shared by its roster agencies, including Proximity and OgilvyOne.
As well as looking after BT Business, WWAV will also be responsible for BT Major Business, where it will manage communications for the company's larger corporate customer accounts.
The review was prompted by the arrival of Tim Evans last September. Evans was appointed as BT Business' marketing director, having previously held the same position for BT Retail.
The direct marketing account is the latest part of BT Business to be subject to review in recent months. Late last year, BT appointed Starcom MediaVest to handle its press buying, and handed Agency Republic an expanded role on its digital roster.
BT Business' creative account is handled by St Luke's. The agency shares BT's creative roster with Abbott Mead Vickers BBDO. However, BT is currently looking for a third agency to join them and has shortlisted Clemmow Hornby Inge, DFGW and Fallon.
The win is part of a good new-business start to 2003 for WWAV. In January, it won the combined £5 million Cancer Research UK account, taking £4 million-worth of business off the fellow incumbent, AMV. Earlier this month, WWAV won the Lloyds TSB Trustcard account, beating fellow roster agencies Partners Andrews Aldridge and Interfocus.