To all the "experts", in theory there is no reason why an "iPad" micro sim won't work inside an iPhone (4) -they are physically manufactured in the same way and are identical in their capabilities. I mean what, do you think they leave the "voice" part out when they are making the sim or something? 
I'd like to know how that happens, lol.
The only thing that might prevent an iPad sim working in an iPhone is the way it has been configured or activated for use on an iPad -or indeed, certain sims could be "blocked" for non-iPad use (by identifying IMEI numbers in use, maybe?).
I just wanted to clear this up as this thread is going around in circles, and to be honest it is getting a bit tedious reading the "expert" opinions of some people, who, quite honestly, don't have a clue.

I'd like to know how that happens, lol.
The only thing that might prevent an iPad sim working in an iPhone is the way it has been configured or activated for use on an iPad -or indeed, certain sims could be "blocked" for non-iPad use (by identifying IMEI numbers in use, maybe?).
I just wanted to clear this up as this thread is going around in circles, and to be honest it is getting a bit tedious reading the "expert" opinions of some people, who, quite honestly, don't have a clue.