That's not entirely true. I'm not going to post any details here, because I seriously question the legality of it, so you'll have to take my word for it (or don't; makes no difference to me)...But there absolutely do exist apps that will change your outgoing caller ID to whatever you want. You won't find them on any app store, and I'd be surprised if you find them from searching Google, but they are out there.
My understanding of the technical details of how exactly they work is fuzzy, at best, but I've tested more than one method with a couple of friends, and sure enough, I was able to call them and their phone showed an incoming call from 911, their own number, and whatever else I set it to via these methods.
Again, I have no intention of providing any further details or any 'proof', but if you're really interested in such a thing, and know where and how to look, eventually you'll find it, as I did.
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That's NOT CORRECT. You'll have to take my word for it (or don't; makes no difference to me).
Do you know any of these terms: ACM, IAM, ISUP, IMSI, TMSI, MSISDN, Ki, Kc, A3/A5.... blah blah? If yes so let's continue talking about it, if no so I dont know how to explain for you to understand.
Again that's not correct. End user never can spoof his caller id, because it is assigned at the remote site (service provider site), not at the end-user side.
---------- Post added at 04:29 PM ---------- Previous post was at 04:27 PM ----------
You can use third party services to spoof number, I on Cydia I remember app/tweak that did it was not a free service.
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Yes, this is the case (use third party services to spoof number). But this is not what the OP was asking for.