All points well taken - and that I have a firm grasp on.

My threat model is "telco or ISP employee decides to see if John is a customer and, if so, just what John does with his phone". They will not find me in their customer database and they'd have to dig fairly deeply, and possibly involve banks and/or LEAs which are not my threat model.

Also, just as a coincidence, and not by design, my place of residence has zero bars of mobile service ... I lose it about two miles from where I live ...