I'm travelling to Guatemala for USA and was wondering about putting a sim card into my old iphone 4 that is unlocked. I saw that Tigo and Claro are good providers in Guatemala and was wondering if there is a place at Guatemala City Airport to purchase one of these sim cards. I would like to be able to use it for GPS and navigation mainly for when I go to Antigua (1st), Rio Dulce (2nd) and Flores (3rd), so I need a data plan. Where can I get a sim card? Thanks!