I found these ads in the 1944 Southern California Telephone Company phone books for West Los Angeles. While I knew about victory gardens, war bonds, loose lips, and butter rationing, this was a new one on me.
Text: "Night-time is about the best time a service man has to call home. That's a good point to remember when you feel the urge to make a Long Distance call between 7 and 10 P.M. If it isn't important, we hope you won't make it. Let the men in service have first call on the wires."
Text: "We appreciate the help you are giving us in keeping the Long Distance lines open for war calls. The production of munitions... the movement of troops... the building of ships and bombers... have put the Long Distance lines squarely up against their biggest task. Materials for building telephone lines are no longer available -- they are needed on the fighting fronts. That is why we ask that only really necessary calls be made to war-busy centers. Thank you for your fine cooperation."
(This one says pretty much the same thing as the one above)
Text: "The trained eyes and fingers of telephone operators are needed, these days, at the switchboards that are heavily loaded with war calls. Telephone equipment of every kind is deep in the war task. Will you help us to make every bit of equipment count? Here is one way: Please look in the Directory for any number you are not sure of. Please look there first before you call 'Information.' Thousands of calls daily, in which 'Information' is asked to help, are for numbers that are IN the Directory. Our foremost job is the war job. It just is not feasible to do all the things for our customers that we were able to do in peace time. We appreciate your understanding and your friendly cooperation.