Android (8.1) Messages app has a phone number popup when message-field is empty

[kattoor]

The Android Messages app always gives me a pop up with a phone number I don't recognize. When I type anything into the message-field, the popup disappears, only to reappear when I remove the entered text.
Any thoughts on why this happens / how to stop it from happening?
I've already tried clearing the app's cache, clearing all data and re-installing.

Honor 10 COL-L29
Android 8.1.0

 

[Rukbat]

Have you tried calling the number to see who it is? (It could be your carrier - or a sales pitch which would make it spam.)