Query about setting up iPhone 5 with new network

[budge9]

Currently I have an iPhone 3GS on O2 network and have just received my new iPhone 5 from T mobile (as I want to transfer to them).
I was advised to call T mobile with the PAC code from O2 once I had received my new iPhone 5 so that they could transfer my number to them and that this should take 1 or 2 days. I am therefore going to call them in the morning to do this.

I therefore want to ask whether I should wait for T mobile to transfer my number over to them before I plug my iPhone 5 in to my macbook and sync it with iTunes in order to put all my contacts, apps, photos etc on it or if I should just plug it in now and the phone number will just change once T mobile put my original phone number on the account.

How will iCloud work as if I plug my iPhone 5 in and sync it then I will have a T mobile phone, presumably using iCloud, as well as continuing to use my old O2 iPhone 3GS for a few days which is also currently set up to sync with iCloud.

Any help would be much appreciated!!!

 

[budge9]

Is it possible to activate iPhone 5 just using phone (i.e. don't plug it in to iTunes), wait for my number to transfer over, and then plug it in to iTunes to get all my messages, contacts, apps etc. as they are on my old phone?!?!?

This one has really got me puzzled!

 

[DefBref]

Your overthinking it and making it seem more complicated than it is.

Just because you restore from backup of your old phone on the new phone, doesn't affect anything on the old phone.

The only thing I would advise is to make sure both phones are named differently in itunes so you can identify each one easily in itunes/icloud.