Sims cell phone bug

Are you using mods in your game ?  If so, please remove them

See this for more information: [PLEASE READ] Usage of Mods and Custom Content 

Same here. I didn't have this problem until the game updated to the most recent patch. It seems like after every update, something else new breaks every time.....I can't use the phone at all. This happens with and without mods.

Try resetting your user files as described in the factory reset described in this post: http://answers.ea.com/t5/The-Sims-4/FAQ-Troubleshooting-Steps-amp-Known-Issues/m-p/3621199

You won't loose anything. Just make sure to not delete any files  and make a backup.

Try on a new game with nothing added back first (start new game). If it works, put back your save game and try again. If it still works, you can start putting stuff back.

• Options.ini (or just re-set all your settings manually)
• Tray Folder
• Screenshots/Videos/Custom music
• Rest of the save games (leave out slot_00000001.save which is the autosave)
• Custom content like clothing, hair, skins, make up ....
• Mods (one by one, making sure they all still work)

The rest does not need putting back, cause they are mostly cache files that recreate or log files that are not needed for the game. 

Resetting it worked.  I don't know what specifically caused the bug though, because I put all the mods back in and all the CC and reloaded my lastest save (from before the reset) and it didn't rebreak. Could it have been because of the Weekly Challenge NPC? I hadn't had the problem until the NPC spawned into my town and now that I've reset, she has disappeared from my game. I guess I'll never really know. I'm just glad that it is back to working again. Only thing now to see is if that random resetting/freezing bug disappears too.

Could be a mod conflicting with her.

Do you have any UI mods ?

It could have been. I have the max interaction mod, the only UI mod I use. She kept getting stuck trying to interact with the mailbox in one of my saves. And I had noticed the cell phone stopped working soon after  I spoke to her for the first time.

Check if there's an updated version of the mod. It's never advisable to use outdated mods