Can i put in a NZ sim card into my UK iphone?

http://support.apple.com/kb/ht1937

Accoprding to Apple's information, all UK phones are sold as locked to the carrier you got it from, so yours is ALREADY locked to T-Mobile (activation has nothing to do with whether a phone is sold as locked or not).

However, it looks like, from Apple's listing, that they also support unlocking, but you will need to contact them about doing that. There may be restrictions, like so many months under contract first, or a fee, or whatever rules they apply to unlocking. Or there may be none and you just need to ask them to do it.

Regardless, you need to contact T-Mobile and ask them about how to get an unlock request processed by them. And do it before you leave - much more difficult to deal with once you are far removed from their network.

Any T-Mobile (UK) phone you purchased is carrier locked to T-Mobile UK and won't work with any other carrier or SIM card other than Vodafone UK. They won't work in NZ with either. T-Mobile offers unlocking so that it will work with other carriers. Likely you'll have to pay for the unlocking as you never used them for service.

If you have just bought the iPhone from T-Mobile then I suspect it is locked to that carrier. You will need to speak to the carrier to request they unlock it or if it is still within the 30 day warranty period, return it and purchase an officially unlocked iPhone from Apple. You will then be able to use the iPhone in both the UK and NZ with any supported SIM.

If you can return it I recommend doing so, it IS locked to T-Mobile

they only sell locked iPhones .The only source of unlocked

iPhones is Apple retail

T-M will unlock but IIRC insist it will take 30 days ( no compromise)

and there is no telling whether they will unlock a new one with no usage

The last person posting here was going abroad and needed T-Mobile

to unlock the iPhone but T-M insisted on taking 30 days from request

You will time out as this iPhone was unlocked but only after 30 days and on her

return and you have the initial period which may be 30 days or whatever

Your iPhone but if you can take it back I would ,a genuine unlocked iPhone

will work anywhere on a GSM Apple approved network

Experience also indicates the process has to be carried out in UK

sadly you picked the most unhelpful of all the UK carriers

Last but not least the warranty is not international iPhone would need to be returned

to UK for hardware faults

I heard if the T-mobile is set to a pay monthly contract I can do this after 30days(unlock) this does'nt seem so bad

Likely, there will be an early contract termination fee for T-Mobile UK, in addition to the unlocking fee. Your contract with T-Mobile UK won't be transferable to NZ.

There's a good chance the total cost will exceed returning this phone before the contract kicks in and buying a full price factory unlocked phone, preferably in NZ where it will be covered by the warranty.