Ok, here it is, Heartbreak Ridge, the movie and here is the part that ACTUALLY happened.

trapped in a building by enemy armor and infantry, the R.T.O. (radioman), Profile (Tom Villard), is killed and his radio is destroyed leaving them out of direct comms. In the heat of action, Lieutenant Ring shows previously unsuspected leadership qualities and comes up with the idea of using a telephone to make a long distance call to Camp Lejeune in North Carolina and call in air support