In general, it's not chargeable. However, some systems get "confused" (intentionally misbill, since the consumer probably won't notice, and the company need only refund the amount of the overcharge, so there is little risk.)
(TELECOM Digest Editor's Note: However, considering that a cell phone is normally always within its owner's reach (a holster fastened to your trousers, in your purse, in a holder near the driver of an automobile, etc) it would seem very odd that it had to ring more than three or four times, at best, unanswered. PAT]