I am a former Department of Transportation employee who resigned in November 2014 to remove myself from a hostile work environment and hostile employees (I am completely deaf).
I looked up the definition of customer service, and here it is: Customer service is the provision of service to customers before, during and after a purchase.
My hostile and uncooperative coworkers successfully complained to my manager that I wasn't providing them with "customer service" during my interactions with them (and I repeat, I am completely deaf).
Two government employees interacting together is not customer service. Government employees all too often use "customer service" as a weapon in the workplace if they feel disrespected, even for arbitrary reasons. This kind of behavior can ruin lives.