GSM units that transmit within high tariff countries (below) will be liable to a surcharge. GSM units will incur a prorated charge up to twenty dollars (20.00 USD) per month per transmitter for the first one megabyte (1 MB) and a prorated charge up to twenty dollars (prorated) per month per transmitter for each additional megabyte used in any calendar month. 1 MB = 1024 kB. List subject to change.