Rules for treating inbound customer calls with respect:
0. Spend a lot more money on this. Hire more agents. Train them better. Treat them with respect and they'll do the same to those they interact with. Have a bright red light flash on the CEO's desk whenever anyone, anywhere, is on hold for more than 5 minutes. If it gets to seven, have the call automatically route to the mobile phone of the CEO's spouse.
1. Have a very smart and very motivated front line. "I'll connect you directly to the person who can help you if you let me know what you need..." Don't have these people pretend that they can help. It leads to long conversations and frustration.
2. 80% of your inbound calls are about the same ten things. First, eliminate those problems in future products, packaging and policies. The best way to handle these calls is to eliminate them. Second, put clear, fun and complete answers to these questions online where they are easy to find. And third, hire talented voice actors to record engaging answers to each, and offer them as a first resort as a result of #1, above.
3. Change your onhold music to Bill Cosby and Woody Allen records.
4. Whenever the wait is more than two minutes, offer a simple way to be called back, and then make sure it works.
5. If you're closed, tell us the hours you are open and the relevant websites. Make sure the information is accurate.
Even famous companies get all of these wrong... Only one of the five steps is truly expensive, and yet all six are regularly ignored by companies that don't care or act like they don't.
(NB it's just fine to make it clear that a call is not important to you. I've never built a company around amazing phone support, precisely because it's so difficult to keep the promise. As far as I'm concerned, it's fine for some industries to not do the phone well. Just be clear that this is the case by routing people off the phone or at least not lying about it).