Yep -- there's a simple answer to this, which is for US interchange carriers to have required as a function of LAW that you cannot set Caller ID to a number you do not own.

That doesn't stop the (very valid) reason to override it; we used to do it at MCSNet on traditional DS-1 service in that when you dialed out you want the person you call to get the "main" front desk number, not the number on the trunk which won't ring anywhere if someone calls it.

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