I*ve seen a similar thing these days on a Customers SaaS-Environment 19.02.0.7 with a couple of Android Devices in Germany, currently in pre-production. Right now no device (there just two, re-enrollment doesn`t do a thing) is reporting back phone numbers. While the devices say ' SIM Card Status Normal' they report back ' SIM Not Detected' under Phone Number in Device View. Guess that`s worth a ticket. Haven't found anything on the Known/Fixed issues in the 1902/1903 notes.
However, the Enviroment is scheduled for update next monday to 1903, we`ll see if that changes the behaviour.
We had the same issue in Australia. We've worked with AirWatch support for almost 2 months they collected heaps of logs from the device also they've tracked the communication between the device and the AirWatch console then they finally said the issue was related to the service provider. They said that the SIM card wasn't reporting its number to the console so they closed the case.
The weird thing is we've got customers that SIM Number is displayed and some that the SIM Number is not displayed. Does not matter if the device is either iOS or Android the issue has been happening with some customer and it doesn't happen with others.