The move ends College Hill's relationship a little over a year after the agency picked up the account.
College Hill began work in March 2004, one month after Business Serve floated on the alternative investment market.
Binns & Co account director Paul McManus said he was hoping to draw the City's attention to Business Serve's position as one of the first companies to offer voice-over-IP (VoIP).
VoIP allows customers to use their broadband internet connections to make cheap phone calls. Customers have traditionally needed an engineer to install VoIP on their computers, but Business Serve has developed a 'plug and play' package that installs the software from a CD-ROM.
The company has more than 1,000 VoIP business customers in the UK.