Definitions for "Enhanced Service"
Services like voicemail and call-waiting are considered enhance services. Most of the time, you will be charged extra for requesting these services; however, they are occasionally offered, free of charge, by a long-distance carrier seeking to expand their consumer base by offering incentives.
Long distance carriers provide services which include voicemail, call waiting, text messaging, and most of the time there are additional charges. Some providers issue these services free of charge as an incentive to build their customer base.
A type of Telecommunication Service that add genuine value to, and contain substantial elements additional to, the basic telecommunications switching and Transmission Network . source: EURESCOM domain:TMN usage