You can assign service zones to customers in the Customer Card window. When you allocate a resource (for example, a technician) to a service task that is to be performed at the customer site, you can then select a resource that is assigned to the same service zone as the customer.
You set up how you use service zones in the Service Zones Option field in the Service Mgt. Setup window.
Open the 
Customer Card window.
Browse to the customer that you want to assign a service zone to.
On the Service tab, in the
Service Zone Code field,
click the AssistButton 
to see the Service Zones window. Select the service zone you want to
assign to the customer, and then click OK to copy the service zone code to the
field.
Repeat steps 2 and 3 for each customer you want to assign a service zone to.
Assigning to Resources to Service Zones