Do you have any other phones in the home? Are they properly "hung up". Unplug the phone line and plug it back in. If it's a cordless phone, unplug the base station from the phone line and also from power. Wait a minute and plug everything back in.
If you have one of the older style phone modems, unplug it for a minute and replug it so that it reboots.
If you have the newer IgniteTV gateway, do a restart of the system via the WiFi app. This will also bring down the Internet and TV for 5-6 minutes. Unplug/replug is also an option.
I appreciate you trying all the suggested steps. Are you on the legacy system where you have a dedicated modem for your phone service?