The agency will provide alldayPA with comms strategy advice as well as PR support.
It is the first time the Manchester-based answering service has hired an outside agency to provide comms advice.
Chameleon chief executive Tom Berry said alldayPA had invested £11m in technology and expansion plans, and represented a new wave of "home-grown success stories".
He added: "AlldayPA is much more than a call centre – it provides brilliant call answering, crisis response and essential order fulfilment services to entrepreneurs, owner-managers and self-employed professionals. We are incredibly proud to have been selected to help alldayPA transform its corporate colours."
AlldayPA chief financial officer Ken Crabtree said the company selected Chameleon because it demonstrated an understanding of its service.