interesting that @josehill was able to port a landline to a mobile phone.
Maybe that’s only possible in the US?
I have asked providers about doing that here in Germany but am told it’s not possible. Even when I explain, the ‘landline’ is not the traditional kind but comes over our DSL connection, which I plan to shut off and replace with cellular data. Companies I’ve asked just dismiss the question without really listening, I have the feeling. Web sites I’ve found are also vague. Maybe it has to do with contracts or something, I prefer prepaid to long term contracts so maybe it’s only possible with the latter.
Will probably just go through the porting process and see if it works.
The US liberalized its telephone laws to allow porting between most mobile carriers in a given region and between land and mobile carriers in 1996, though it took a few more years for the associated regulations to catch up.
There are some numbers in the US that can’t be ported, but I’ve been able to port nearly every number I’ve tried. In the USA, FAX numbers sometimes can’t be ported, and at least a few years ago, the Google Voice system seemed quite a lot more limited than others. I don’t know if that still is the case. When porting to/from VoIP services, I understand that the VoIP service must have a physical switching facility within the region of transfer, though I don’t know the details.
Unlike the US, many countries use entirely different “area codes” for mobile numbers than landlines. Billing in these countries often relies on this distinction since the caller always pays (or has minutes taken from their allotment) and is/was charged extra for connections to cellular, never the recipient.
The area code in this system serves as the distinction letting the caller know about the increased rate that will apply, like toll numbers with their own prefix or the country code telling you that you are about to be paying international calling rates.
In the US we don’t use area codes that way and there is no provision for directly recognizing numbers as landlines or cellular. One consequence of that is that the mobile recipient pays or has minutes taken from their allotment when called, a concept rather alien to most other countries. Obviously, this is all a bit historical (or at least becoming more and more so) because most people increasingly have all-inclusive plans where you don’t have minute allotments and pay flat rate rather than per call/minute.
Once upon a time, your phone number was an actual index referencing a physical location in the phone switch network. An area code represented a large region. The first three digits after that represented a physical “exchange” (central office, and often a specific rack of equipment in that office) and the last four digits represented a port on that rack. So a given location could not change numbers to something outside the block assigned to that location’s exchange. And if you move to a location served by a different exchange, you would have to get a new number.
But that hasn’t been the case for a long time. The modern voice network uses a completely different form of location-based address. OSI-based networks use NSAP addresses. I’m sure there are other kinds of addresses as well, depending on the underlying technology used by a service provider.
Your phone number is actually a key used to look-up the underlying address, which is then used to actually place the call. This is similar in concept to how the DNS system looks up IP addresses from host names. This is what allows you to port a phone number (pretty much) from anything to anything - once the endpoint for your new account is created, the actual transfer is just a matter of changing the address that your phone number maps onto.
If a phone company says your number can’t be ported, then that is for administrative reasons (policy, billing, regulation, etc.) and not for any technical reasons.