I worked as a telephone operator a couple of summers and pay phones were a pain in the ass. The protocol for a long-distance call (and this was back when long distance was expensive, up to to a couple of dollars/minute), you'd collect for three minutes up front and refund if they went under. If the call went longer, the caller was expected to stay on the line and pay the balance, which could be considerable. Often they just bailed. There was one exchange near a military base where we'd have to handle lengthy long-distance calls from lovesick/homesick recruits, and so many of them bailed out at the end of call that we took to breaking in every three minutes to collect more coins. Worst part of the job.