In 1965, at the age of 20, I was living in Paris.  It was very expensive to call the USA.  My friend, Mike, and I heard that there was a tape recorder that had just hit the market in Germany which was portable.  So we went to a German border town. I don’t remember the name but the hotel we stayed in was called the “Bunker Hotel”.  You get the picture!
In those days, the telephone operators knew how much you deposited by the sounds of the different kinds of coins.  So we recorded the sounds that were needed to make a 3 minute call to the USA from Paris.  Then when the operator said (in French of course), deposit x number of Francs, we played back series of sounds.
The second hack, was by passing our electric meter.  We lived in a building with a concierge.  The meter reader would come by one a month.  We would get a notice from the concierge that if we were not home we should leave our key with him so he could let the meter reader in.  I would un-do the by pass. When the meter reader arrive, he would see that we had used no electricity (we had jackets  and candles).  The good news was that we had an electric hot water heater and a shower (which was very unusual in Paris at that time).  We put up ads at the Paris Conservatory of Music (where we were both taking classes) that we would provide any female students with free showers.