Billing increment refers to the amount of seconds that calls on a long distance phone call are rounded up to. For example, many plans have a 6-second billing increment--after the first 18 seconds (a common minimum call length).

Thus, a 10-second call would round up to the minimum call length of 18 seconds. A 20-second call would round up to the nearest 6 second total, which would be 24.

Quite a number of calling plans can have billing increments of whole minutes. Check your most recent phone bill to determine what size billing increments come with your current long distance plan.

http://www.lowest-long-distance-rate.com/billing-increment.h...