You can assign a session to a campaign in order to contextualize calls in a given campaign or to change or remove the campaign's context. This operation is important for Contact Center administration and performance monitoring.
Suppose that you receive a call from campaign A. After talking to the customer, you find out that the call should belong to campaign B. Since you have the skills needed to answer the call on campaign B, you do not transfer the call to campaign B; instead, you assign it to campaign B and carry on answering the interaction.
The session can then be associated with a campaign by clicking the Assign Service button 
and selecting a campaign from the drop-down list.