Congratulations on your new role, sounds like it will take a lot to get to grips with everything if it is a new department.
There are a great deal of options when it comes to service audits and measuring how effective customer service is. However there are two key areas, one is a process audit and the other is how happy are customers with the service they receive.
The audit is easier to manage as it requires someone checking that all the things that should happen, do happen. The second is a little harder as it requires direct feedback from your customers.
For the first you can do this internally (or externally via mystery shoppers) but needs you to understand what your processes are (which i think is the basis of your question). This will require some hands on time by your self and your colleagues as you need to fully understand what your processes should be, and then measure if the retail service centres are actually delivering these.
Your short question actually has quite a detailed answer and if you would like to have a chat then please feel free to email me at firstname.lastname@example.org
I have helped other companies set up these types of measures and perhaps i can be of assistance to you.