e.g. does the prefix (07799) tell me who the operator is? I know people transfer numbers so I'm guessing the answer is no

No is indeed the correct answer.

well, 07799 was originally allocated to Voda but the user [as you thought] may well have had it ported to another network

Phone it and hope the owner of the number doesn't answer. Call will probablygo to voicemail and if they haven't changed the default greeting, that will tell you – probably

079 tends to be t-mobile
voicemail might be a good shout though 😛

used to be the case but since you can migrate your number anywhere, it's not possible anymore.

You can in Iraq. Are you in Iraq?

079 tends to be t-mobile

my orange number started with that.

This will tell you which network the number was originally allocated to:

http://www.ukphoneinfo.com/locator.php

However, as said, people can port easily to other networks. I've had mine over a decade and it's been on all of them at some point.

My and Mrs Grips' Orange numbers both start with 079.

I seem to remember that way way back when mobiles first started there was allocation of prefixes to operators, but they very rapidly started to run out of allocation so it ended up a free-for-all I think.

thought as much. Never mind.

ta

Orange was originally 0973, then they added the 7's to all mobile numbers thus Orange changed to 07973. Then loads of "area codes" were assigned as mobile use went even crazier.

I've had same number for 13 years or so, first orange, then tesco, now vodafone.

Orange was originally 0973, then they added the 7's to all mobile numbers thus Orange changed to 07973.

My Dad's mobile number did that, went from 0973 to 07973. My Orange number which I got about 13 years ago was 07977, I bought my first mobile just before that rule about all mobiles having an 07 prefix came in.

I've been on Orange for a loooong time, with the same number.
It starts 077………..

My wife is on Orange too, guess what, her number starts with 077 too.

It looks like Operators use more than one prefix then…

079 tends to be t-mobile

I'm 079 and I'm with Vodafone

mine starts with 077 – was originally with orange, then went on to o2, how I loved people phoning me up at contract changing time telling me they wanted to talk to me about my orange phone. Cue long pause & me confused sounding telling them my phone is black not orange, & how can they tell what colour phone I own.

How they laughed.

my number is 0799 and that was o2 until i changed it to voda

You used to be able to tell (sometimes) by default voicemail message which network a phone was with, although that means phoning them at 2:00am to make sure they don't pickup 🙂

You can tell by putting the number in a website. Try googling magsys online codelook or something similar. If the number has been ported to a new provider it can take a little while to change but it's fairly accurate.

My number prefix is 07870, which started off on Orange, then got ported to O2. For ages, actually several years I regularly got cold calls from Orange dealers trying to get me to upgrade my Orange phone, to which I'd reply, rather puzzled, 'but I'm on O2…', to which they'd say 'ah, right, I'll take you off our list'. Haven't had one for some years now. Oddly, I've never, ever, had a cold call from O2, which encourages me to stay with them and never, under any circumstances, go back to Orange.