Some of the key advantages of using a SIP trunking service are cost savings, scalability, flexibility, and added features such as voicemail, call routing, call waiting, call forwarding, IVR. It allows users to make and receive calls over the internet at a lower cost than traditional phone lines, easily scale telephone service up or down as needed, reroute calls to other numbers or locations in case of an outage and add more advanced features to improve communication experience.