Challenge based testing

For phone lines that are making unusually high number of calls during an hour, an automated message should come on asking it to type into the key pad a randomly generated 2-4 number to confirm it is a human. If the number is typed incorrectly or not typed at all 3 times in any 6 months, that line is flagged and/or put on hold from making outgoing calls until speaking with a phone company. You would have 2 tries to get the number correct.