You have two cost structures for paying for conferencing calling services – pay-as-you-go and a flat monthly fee. Reservation-less services typically charge 2-10 cents per minute, while pay-as-you-go plans incur a per-minute fee for each participant.  Pay-as-you-go is probably the most flexible option, as it allows you to pay only for the time that you use the service. However, rate plans vary from provider to provider. Research the industry standard for per-minute and per-call rates to know where you stand and estimate the potential expenses before making a decision.