I have had this happen in my game. Basically something glitches in the game and causes the phone to be wonky. There's a couple of tips to try to fix this, (and more below this). You can either try resetting household, evicting the household and moving them back in or use MasterController to reset everything.
If that doesn't work you can go back to a previous save, if the problem just happened fairly recently and you have a save from before the problem started happening.
Reset Town, Individual Sims and/or Evict Household
http://www.carls-sims-4-guide.com/forum/index.php?topic=20732.msg401812#msg401812Go Back a Previous Save File
http://www.carls-sims-4-guide.com/forum/index.php?topic=20732.msg433992#msg433992On further searching on the problem I have found some other tips:
1. Have Sim change clothes via the dresser or take a shower.
2. Visit a rabbit hole like the bookstore, movie theater, gym etc.
3. If the Sim has a Showtime gig, see if it can be canceled. As it seems the proprietors either don't exist any more or have glitched in some way.
4. If it just happened, don't save the game. Exit the game
without saving. Load the game again to see if the problem is still there. *If you've been playing for a long time, it's recommended to restart the computer to help refresh it's memory.
5. Check to make sure it's not a conflict with a mod by going through the mods you have.
