If your business deals with customers via telephone, and you would prefer not to piss your customers to hell off:
Do not have a robot answer your phone, and then ask customers to tell it what they want. These systems do not work for any but the most basic requests. You will annoy your customers less by asking them to push buttons in order to navigate a menu tree. Really.
Do not ask your customers to push a button in order to select an action without giving them at least ten seconds to do so. Many if not most people are calling you from a cell phone (and many of the rest from a cordless handset). They need time to take the phone from their ear and press the key. If they're smartphone users, they may also need time to turn on the keypad. And if they want to hear what you say after they press the key, they may also need time to turn on speakerphone. Doing all those things as quickly as possible only to discover that you've been hung-up on is seriously fucking annoying.
If you're using a computer voice to read sentences to people
Spend some money on a good one
Use it to speak entire sentences to your customers. Do not record it saying sentence fragments with blanks in them, and then have it speak individual words into the blanks.
Especially do not have it speak into the blanks at a significantly lower volume than the pre-recorded parts of the sentence. While there is a certain entertainment value in listening to a computer mumble, it is not entertaining for long, and not something you want your customers to associate with you.
If you put your customers on hold, tell them how long to expect to be on hold, then play them some innocuous music for the duration. Do not interrupt the music every fifteen seconds to tell them "Your call is important to us." The next voice your customer hears must be a human being who is there to help them. Your customer is a busy person, just like you. The time they spend on hold with you is time they can also spend doing something of value to them. When a voice comes from the phone, it distracts them from that something, and if that distraction is not also of value to them, their time on hold with you becomes a net loss.
In short, even when you are expressing your actions through a computer, do unto others as you would have them do unto you.