Number swap??

[IftiBashir]

I'm currently on a Simplicity 12 month tariff. 

I wish to take out a second line - another simplicity 12 month tariff. 

If I do this, can I swap the numbers around on both lines?

i would want my new line to have my old number, and the old line to have the new number. 

Is this possible?

[Anonymous]

That's not a number swap, that's a number "transfer"
What I asking is to keep to ACTIVE contracts, and exchange the numbers.
What you must of done, is transfer the OLD number to the NEW sim, therefore making the old sim cease to exist ending your old contract.

I have 2 new contracts, I don't either either to expire. I simply want to swap the numbers around. They don't do this, becuase they say to move the number will expire the contract it's leaving from...

I called up 4x last night and each time they say it's impossible to swap numbers around while keeping the contract active. 
I've called up a total of 9x over the last year trying to get it done, they say it's technically not possible everytime.

[Anonymous]

Well I got an O2 contract, not for the contract but for the phone, last year.
But I thought I might as well use the contract while I had it.
200 mins, unlimited texts £322 over 2 years including Samsung Note, which was a good deal, because at the time the Note was £400 sim free... So I basically got a £78 saving + 2 years of 200 mins a month.

Now I've found a voda contract 
£9 a year, after quidco. (They have £100 cashback on Vodafone, yes, I'm a network **bleep**, I have no loyalty, although if I'm honest O2 have the best service and best Customer Service, so I advice going with them, unless you're a deal junkie like myself...)
300 mins + (500 voda to voda)
unlimited texts
250mb data (first 3 months unlimited, this will be handy as I have a Nexus 4 now, only 8gb, so cloud services will be made use off, until I get the Sammy S4 anyway.)
750mb wifi

So I now wish to make the voda my main number (with the number I like, which I've used for like 10 years), however the only way to do that is transfer my O2 number to voda, but that will end the O2 contract which I have 15 months left on, I wanna keep that and give it to my dad, without him having my number...

So they definitely don't do number swaps cross networks.
So that's why it would be a good idea to have a 3rd sim in the game, a pay as you go, and then O2 could number swap the PAYG with the O2 Contract, (but they claim this is not technically possible) and then later of course, transfer the PAYG with the other network, expiring the PAYG instead of the o2 Contract.

To your sigature question.
Use Nexus 4 until S4 is out, I have a Nexus 4, it's a great phone, but bad battery life, no micro sd, poor camera, and no 16:9 photos, unless you use 3rd party app, and no video calling via 3g, which of course only O2 give free mins for, but unable to use them.

[MI5]

OK, I understand what you are wanting now, but I've never known it to be possible, on any network? Thanks for the comments re Nexus 4. I am waiting delivery from Google, but really like the xperia z (from the reviews), so I might get one of those too, but then of course I will want the S4 when that comes out also