When CallFire executes an answering machine only campaign, it must hang up on live answers. As a general rule, it is not permitted to hang up on live people if you are calling residences. Fines can be severe if you hang up on consumers. For this reason, answering machine only campaigns are almost exclusively used for business to business calling. More information can be found here.
Because CallFire must complete every phone call in order to determine if the recipient is a live person or an answering machine, you will be charged for all live answer calls in an answering machine only campaign. CallFire must stay on the line for several seconds to determine if it has encountered a real person or a machine. If it is a live person, no message will be left, but you will be charged for the connected call.