Record yourself to improve diction, inflection and vocabulary. It's amazing some of the things that we say that we don't even hear ourselves saying. By recording yourself you'll be able to spot many of the concentration barriers that are often in your telephone conversations. You will be amazed at the number of times you say ahhh, hmmm, or repeat phrases, all of which breaks the rhythm and pattern of the listener's attention. If you have any doubt, ask the person to pronounce their name for you.
People like to hear their name and they like to hear their name used correctly.
If you have an unusual name, you should pronounce it in a way that makes it easy. Be sure they know who you are and how to pronounce your name. If your call is to follow up a letter and the letter has not been received, confirm the address and continue the presentation. You should simply state what the letter was about. This gives you the opportunity to turn a less productive call into a more productive call.