An SLA can define an acceptance step, which adds a step to the process for the service provider to accept or decline the task.
If the service provider does not accept the task on time (as defined in the SLA), an escalation occurs.
Declining a service request is not the same as rejecting a service request; a rejection is made by an approving manager and ends the process flow, whereas declining is done by a service provider who does not wish to take on this task.