I think the basic thing is to not call O2 about this ...
I just spoke to retentions, upgrades and customer services and none of would say that if i upgraded to a Simplicity for iPhone 12 months that i would be able to continue to use that tariff on thursday...
They mostly said that they had been given zero policy information on current customers looking to buy their own iphone other than that they had been told that iPhone 4 users should be on a new iPhone 4 contract/tariff
Even when i asked for PAC code they just said they couldn't promise anything and i should call back thursday ... when i suggested this would then render the conversation useless as i would then have no option but to have an iPhone 4 deal then they kinda admitted defeat.
I just wanted to try and get a clear steer on switching to a 12m simplicity £15/m contract on the current unlimited data basis (they did repeatedly mention that the cap won't affect most customers) ... but it seems evident that O2 are in chaos regarding iPhone 4 and unless they're barefaced deceptive they just don't know anything themselves.
To answer you (sorry if already answered as this is a heck of a long thread) I have two friends both brothers in O2 customer services and was on the iphone £45/month plan.
To verify - You can upgrade to simplicity 12 month and retain your unlimited data. If you upgrade by 23:59 on 23/06/10. From midnight or ... hahaha iphone launch day, you'll be hit by the cap come October. Even asking if I could renew my £45/month tariff on Thursday and get a subsidised handset price when I rolled up to the store nope... that counts as a new contract so I'll hit the data cap. So the only way to get an o2 contract with just FUP and not a 'cap' is simplicity or stick with your existing contract and suck up the £499-599 price. They really are using this to ram home their smartphone tariff changes, fair play to them as it's a good bartering chip.
This it seems is because some people are actually raping o2's data network. I thought I was ok at 400Mb/month but then looked at my uploads included and got over the 500Mb/month and have done probably every month since the 2G launch with O2. They're putting the cap in place because about 20% of users are taking up 90+% of the bandwidth, some are using up to 9-10Gb a month (wtf are you downloading? Or running a sim-powered 3G wireless router??) so new customers are being capped. If you're on an old contract and don't take the p1$$ it's just like any ISP 'fair usage policy' akin to BT's broadband, talktalk, NTL et al.
I've just transferred to the £20/month 12-month simplicity deal, triple checking that I won't be hit by the data cap in October and also that I still get my friend's discount (mmm £14/month for 600 mins, unlimited data+txts) and resorted to buying sim-free this time around from Apple, to save in the long-long term I don't think I'll be moving off this contract.
Also to make you aware that moving from a 30-day simplicity deal to the 12-month equivalent to save £5/month counts as an upgrade so if you did that post 23:59 23/06/10 you'll be hit by the October data cap.
Also micro-sims are still being sent out they're wading through the mailing list and posting them out but you can get one from in stores on Monday.
I did actually ask if they knew if I just waited and got a micro-sim from the Apple store when I bought sim free, got home and 'activated' it on my iPhone 4 - that's the part where it locks the phone to the network - if my sim-free phone would then be locked... they said they didn't know for sure on that one

so I am definitely getting a microsim and activating it in my 3GS before it goes anywhere near my iPhone 4.
HTH, apologies for length or if repetative. I've had 4 hours sleep since Friday
