Not just locally on the device! There must be an error when calling or texting the number.
Data must work for internet for Signal, VoIP, etc.
This is for a UK PAYG SIM.
There should be no way for anyone to demand my number, or for me to leak it, or doing so should be irrelevant as it does not work.
Yeah but like I said, anyone who calls you will just hear the “busy” tone or direct to voicemail. They won’t get the “invalid number” tone like OP wants.