RoIP Walkie-Talkie 2 way radio solution

I need a couple of radios (about 60 handheld walkie-talkie radios) to be used by static security guards in a certain location. We have access to cellular coverage by Digicel PNG ([login to view URL]) in the area. I need a RoIP solution that is cost-effective. I need the cost of handheld walkie-talkie radios, base stations, vehicle radio (x5 vehicles), etc… Please give a solution and estimate the cost so that we can discuss it further.