Common courtesy costs nothing they say. After all “manners maketh man”.

Using correct names on the telephone system is also critical. We like to hear our own name said but it must be said correctly. You cannot address an individual as Mike if he introduced himself as Michael.  

Being polite on the telephone includes being considerate. So remove any of your colloquialisms and TLAs (that’s Three Letter Acronyms) that may cause confusion. Speak clearly and not too quickly. Do not mumble or rush your introduction. If you are making a service call take extra effort to appear helpful no matter how much you are perhaps unexpectedly being put through the mill by others.  

Also, end your calls without the usual telephone handset clatter:
You can always tell when the telephone is banged down on you. There is the noise as the telephone handset is slammed against its cradle. There is an inference that the calling party is disgruntled, aside from the fact that it is deafening and offensive. Even gently putting a phone down can be quite loud to the caller. So this can be misconstrued to be "slamming" when it is no such thing. Preferably use an answer/release key if you have one on your telephone handset. It makes for a more subtle ending and nobody is offended. If you don’t have this facility then press the receiver button down with your finger before hanging up the telephone handset.

Politeness is free.  Impoliteness loses business for you and the company.

Don't forget that Business Telephone Systems are your main means of communicating with customers.  Use them effectively.