What is the difference between Iridium Extreme 9575A & Iridium Extreme 9575 (GSA) & Iridium Extreme 9575

Hello,

I’ve recently discovered various models of the Iridium Extreme Satellite Phone available for purchase at SatellitePhoneStore. Each model comes with a different price range. Could you please assist me in selecting the appropriate device?

Could you please provide information on the differences between the Iridium Extreme 9575A, Iridium Extreme 9575 (GSA), and Iridium Extreme 9575?