IsatPhone Top-UpsIn order to stay connected to one of the world's most reliable and far reaching satellite networks, you need to ensure your IsatPhone is equipped with enough airtime credits. That's where IsatPhone Top Ups come into play. ISatPhone top ups are suitable for IsatPhone Pro and IsatPhone 2. Useful Information Inmarsat SIM cards start with zero balance and validity. A top up's validity period can be extended at a later date by purchasing another prepaid