>>>I have a request to allow a user to enter a cell phone number for sending a sms message. I can make it all work except I can't find a way to figure out who the cell phone carrier is so I can complete the address. Anyone know how to do this?
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>>Users can move the same number between different carriers, so it would be difficult.
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>>Is it possible to just add a field for the users to choose a carrier?
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>But Skype does it, somehow. Are they storing the carriers' dialing ranges, or what? That'd be one very large table. I wonder how do they do it, and if it's a table, how do (did) they fill it.

Dialing ranges would sort of help.
However, I can have a number that from Verizon and then take my number with me to T-Mobile.

Another alternative is to just TRY all the permutations of how to send the SMS via email.
One of them must work.
You could even log the permutations that errored so you don't try them next time.