This GDF soldier is actually a spy working for the Hood and the Chaos Crew. He was first mentioned by Kayo in Signals Part 1 as she suspected the Hood having a spy within the Global Defence Force, and her suspicions were indeed correct as Havoc received a message from their spy when the GDF got a strange request from International Rescue to switch off their space-junk laser.
Later in Break Out, the GDF spy listened in on the conversation between Lady Penelope and Colonel Casey, and informed the Hood and the Chaos Crew about Jeff Tracy's survival and their request to free the Mechanic.
In The Long Reach Part 1, the GDF spy was most likely responsible for the communication hack between International Rescue and the GDF, under the orders from the Hood.
Only appearing once throughout season 3, it is unknown what became of this GDF solider. Likewise, his real name was never revealed. He was voiced by Kayvan Novak.