When potential customer calls your business they are expecting the same courtesy that they would get as if they had walked in your place of business. Customers also expect the person on the other end to be knowledgeable about your product and services or at least direct them to someone who will answer their questions.
If the person who answers the phone has an attitude or is unaware of your products and services you need to keep them away from the phone! They can be costing you money! A customer that has a bad experience with your staff over the phone may take that as an indication of how your business is operated. There is little room for error when it comes to phone etiquette.
Make sure to train your staff on how to handle incoming sales calls, who to direct them to and how to maintain a friendly demeanor on the phone.