look in the iphone thread lots of info there
But you need to ensure you have backed up and synced in itunes first.
You will keep the same number.
You will need to follow the instructions on the simswap page links in the iphone thread sitcky.
Once number swapped to micro sim activate new iphone and setup as old phone not as new all will be put back on the iphone as before apps texts etc.
Then you can erase the old iphone and do what you like.
Asuming you have an iphone.
If not you need to copy contact to your pc using your old phones software or sync with outlook etc that itunes can sync to.
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My first mobile was in 1995 a CM-R111 from sony on Cellnet.
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