Unable to Dial Mobile numbers intermittently

[AndyMacDL]

We have a situation with a user where he can call a mobile number one day and then the next day when he dials the number the line goes dead as though the number hasn't been dialled. 3cx logs just show as not answered

This is the only user that has reported this, and it's happening with various mobile numbers on various days, so there is no pattern. His colleagues can dial the numbers fine

Has anyone else experienced this?

 

[Saqqara]

Outbound rules are the same for this user, compared to one that works fine.

I would see if the line provider can see any traffic on the line, when the call fails.