Hi daniel12 ,
Good day.
Have you checked this matter with another different operator SIM card?
Please kindly help me disable SIM and enable again.
I would also suggest you can update the firmware to the latest WW-15.2016.1903.511 for a check.
(settings> system > system update)
If this problem still appears, please kindly try to backup phone files and factory reset.
Sorry for any inconvenience.