Iridium Satellite Phone Monthly Airtime Service Plans offer the benefit of uninterrupted service, overage on minutes, pay as you go plans, USA and International local phone numbers, rollover minutes, unlimited Iridium to Iridium calling and more.
Iridium Prepaid Plans are more expensive, have a limited amount of minutes, no allowed overage (service will just cut out), no USA or local phone numbers, and minutes can be rolled over only if a new prepaid plan is purchased before the old SIM voucher expires. Monthly service is always recommended for Iridium satellite phones.