Is there a minimum time before you start charging someone for a call?

Yes. In order to make sure that the people in a conversation are able to talk without being disconnected or that the quality of a call is sufficient, the minimum duration for a call to start being charged is 20 seconds. If you speak with someone for less than 20 seconds, the system will consider that the quality of the call or the reason behind the call was not sufficient to start the billing process and no money will be charged.