[cookie_monsta]

Some countries allocate set prefixes to carriers which can be reliable if number porting doesn't enter the equation:

https://en.m.wikipedia.org/wiki/List_of_mobile_telephone_pre...

[barbazoo]

That list isn't very useful in this context unfortunately. There is no reliable mapping between area code and provider in North America.

[cookie_monsta]

That's why my first two words were "some countries". The US is but one.

[ant6n]

Until the number gets ported to a different provider..

[cookie_monsta]

Oh, wow. Which is why my last 7 words were "if number porting doesn't enter the equation"