Once when I worked in customer service, I got in huge amounts of trouble because a customer called head office to complain that my attitude was not as perky as they would have liked. (I’m not kidding. My manager agreed it was totally bogus but he had to write me up anyway.) At that same chain, a colleague got a promotion because a customer called head office to joyously rave about how he went out of his way for them (in a way that all of us regularly went out of our way for customers, it’s just that most of them don’t call head office).
Customer calls matter a lot to some companies. If you think about it, it’s the only way they can really get feedback on their employees - co-workers, managers, subordinates, etc, can’t know what someone’s customer service skills are as well as the customers themselves.
And I know that when I was a customer service wonk I was THRILLED when my colleagues or I got well-deserved customer complaints. It was the only source of recognition for good work (especially in a corporate store), and it was good vindication for bad work - if I was stuck working with someone who couldn’t do their job, the manager was clueless and there was nothing I could do about it. I couldn’t believe some of the crap our customers took from some of my co-workers and they should not have put up with it.
So I do comment about customer service regularly, good or bad. (Note: I NEVER call for the termination of employees. That’s just wrong. I am generous with praise where called for, and I am generous with the benefit of the doubt when my experience was negative. Also I am always, always as sweet as pie; even if I’m angry, it’s almost certainly not the person I’m talking to who deserves my anger.)
Most recently was last week, I went into a big famous store and got really awful service from the first person who “helped” me and really great service from the second (and in the end they didn’t stock my size so I didn’t get what I went in for). When I got home I wrote an e-mail to their info@ address on the website and got a personal reply within a day from head office, and another reply within another day from the manager of the two people I commented about.
Sometimes you even get free stuff. But people who complain just to try to get free stuff are dicks. (That’s a whole nother thread, I think.)
In your case I’d talk to the manager, if only to say “I’ve switched branches and thought you might be interested in hearing why.” I expect the answer would be a “Yes, I’m interested.” If it’s just a matter of slow-ness, nobody is going to lose their job, and it can only help the branch.
On preview I totally agree with what Harmonious Discord said: complain about the length of time to get service, not about the slowness.