Here's a photo of a lovely Metropolitan police mug my mum got from a charity shop, because of the strange slogans on it.
It might be a bit annoying sometimes, to be reminded by a rather chunky mug of 'Service with a Smile' when you're at work. Especially if you feel more like 'serving with a snarl.' It's quite difficult to be nice all the time in jobs where you deal with 'the public'. Such as working on an IT Helpdesk...listening to people complain about their computer problems all day, every day, with varying levels of exasperation and rudeness. Paid to be moaned at, about stuff out of your control....
I had a really crap temp job once, working on a BT freephone line, every workstation in the office had a notice telling you to 'speak with a smile' because people could apparently hear it in your voice. Good customer service. Even when the ubiquitous telephone sleazeballs rang, asking about your underwear or more explicit streams of obscenities...all part of the job, but you still couldn't be rude to them. The sort of job where the door had to be specially unlocked for you to go to the toilet and then they timed you, to stop you taking the piss. (oops- bad pun, but very appropriate.)
Only stayed there 2 weeks, surprisingly enough, I walked as fast as I could every lunchtime in the opposite direction but then had to go back again, until I begged to be moved to another temp job. Well, not quite begged...I don't do that, but you get the idea. But some people do jobs like that every day, so don't be horrible to them on the phone, they don't deserve obscenities or rudeness.