What is a VoIP Service? Brandon Di Perno April 17, 2018 17:09 Updated A VoIP Service is a telephone service that allows subscribers to use a high-speed Internet connection to carry telephone conversations. A company that offers VoIP services is typically referred to as Internet Telephony Service Provider (ITSP). Related articles How do I reach 911 services? Is it different with VoIP? Where is babyTEL available?