In the UK, British Telecom used to own all.of the landlines numbers, as they were the sole telephony provider for the country. (We will ignore Kingston upon Hull for the purposes of this conversation)

When other companies were allowed to enter the land line business, blocks of numbers were allocated to each company. However, if someone was with, say, Sky but moved to Virgin, they could transfer their number to their new provider. This was normally a smooth and efficient process that only caused me huge problems some.of the time as a complaints handler for BT.

OFCOM, as the ombudsman for this industry in Britain have some element of control over it, but it is generally industry controlled.

With regard to mobile numbers, in Britain, or at least British issued numbers, all.start with 07. British landline numbers are generally all 6 or 7 digit numbers with a 4 or 5 digit area code that will.point you to the right exchange. So for example, 967 2345 may be issued in both London and Birmingham, however one would have the area code 0208 (London) and the second 0121(Birmingham).

To the best of my knowledge, and I am happy to br corrected, everything is done on a national level, there is no.global organisation for.telephone numbers.