Change management

Here is a scenario I am under-going , your help is really appreciated.

With 150 seats and a campaign which until recently was purely inbound “Customer service” focus – to a business demand to evolve the centre to more sales focused environment.
I find myself in the position were i need to create a plan to evolve the environment with as little impact as possible to resource and output.

How do you feel this should develop?Have you had experience in the past?

Thanks in advance for your guidance.

CJ