Hello,1) Get a caller-id box and don't take calls from anonymous callers.
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>My local pizzeria has a little problem:
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>"People call in to order pizza's, but they never collect their pizza's".
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>The guy is trying to figure who these people are that never collect their
>pizza's.
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>These people are using:
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>Mobile cell phones.
>And even Skype systems ?!
>
>The pizza guy tries to do it as follows:
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>"Write down customer numbers, and sometimes call them back"
2) There are reverse look-up databases around which can be used to get an address which belonges to a phone number. If the address doesn't match the number, skip the customer.
3) Keep a database with people that ordered before and see if their addresses match.