I got a new Iphone for xmas, I already have a Blackberry Curve. We added another line to our family plan to get the iphone, I would love to be able to keep my phone number from the blackberry. Is it possbile to switch the sim cards between the iphone and the blackberry?
Yes you can keep your number but you won't be able to use your current SIM card as the iPhone4 uses a micro SIM.
The best is to just stop by an ATT store and have them give you a new microSIM programmed with your current phone number to use in the iPhone.
You could attempt to cut your current SIM card down to match the form-factor of the micro-SIM but no reason to do that when ATT will swap it for you.
Also when your at the ATT you can have them switch your data plan to an iPhone data plan so all the features (visual voicemail for instance) works properly. They can also remove the iPhone data plan from whatever line it was that was added to the account. That new lines data requirement (if required) will depend on what type of phone you decide to use on that line.