So, we'll get them set up to dial 800-xxx-xxxx on 320 lines, all at once

When I was working in the telecom industry, I did some work on a predictive dialer system. One of the more amusing bugs (thankfully we spotted it before the code was released) was this:

1. The dialer software would run through a database table of 'prospects' and dial each one.
2. If the software was configured to add a prefix for an outside line, it would add this before dialing.
3. If the call wasn't answered, the number would get put in a different table in the database (subject to expiry time, number of attempts, etc.). This would include the prefix.
4. The call would later be retried from the second table, and the prefix would be added again. If it failed again, back it went, including the (now doubled) prefix.

When you consider that most offices in the UK use '9' for an outside line prefix, we were lucky to notice while it was still on our test system, otherwise we'd have been generating about 5000 calls/hour to the emergency services...