Lobster submitted this idea :
> Just about to give notice to close my O2 contract at 11 months, and will then
> seek out and take up another cashback deal. Looking around tentatively, it
> seems quite likely I'll want to go for another O2 one in fact, which makes
> life a bit more interesting as regards keeping my number.
>
> I've read various reports on this ng of how to do this, using a PAYG service
> as an intermediary. What I was considering doing was as follows:
>
> 1. Give notice to O2 and ask for PAC code today
> 2. In 2-3 weeks, open a new O2 contract which will run alongside the first
> one (I don't care - it will be free anyway!) with a new number
> 3. PAC out to an existing Vodafone PAYG sim card (already up and running in
> my name, last used months ago)
> 4. After a couple more weeks, after the original O2 contract has closed, PAC
> from Vodafone to the new O2 contract.
>
> Will that work, in that the new O2 contract will have been up and running for
> 2-3 weeks on a new number? Or can you only PAC in when you are setting the
> account up? The idea of doing it that way is that the two O2 contracts will
> overlap and I can avoid having to dial out on PAYG for a couple of weeks (any
> incoming calls will go to the Vodafone SIM, in a spare phone).
>
> (By the way has anyone ever heard of cashback deals being invalidated by
> changing the number after the contract has already started?!)
>
> Thanks
> David

Not sure Vodafone allows porting in at anytime. Your O2 account will
close as soon as the number ports out, so no need to wait a couple of
weeks.

I ported to Tesco Mobile earlier in the year for 10 days and then
ported back to O2, was on Tesco for 17 days in total. Had a small
problem with Voicemail as apparently they forgot to port the voicemail,
so callers were still getting Tesco voicemail despite the fact I was on
O2, I know they share the same network.