No Dial Tone

Tried to use our phone today and when we picked up the receiver there was no dial tone on any of our phones.  We have internet.  When I restarted the modem the phones told me to check the line, so I know the phones THINK they are connected to the modem, and when the modem was finished rebooting the "check phone line" error on the hand sets and base station went away.  Still no dial tone.  My XFi app tells me there aren't any service interruptions.  

How do I fix this.