Not many great memories from that era (I was a late teen when payphones largely started disappearing because cell phones) but when as a pre-teen I learned that you could take a standard issue tack from any bulletin board and hold it in contact with the mouthpiece and any other metal object to make free calls, it opened doors in my world forever.
Fact that any major series of companies released tech this easily circumvented gave younger me an intuitive understanding that capitalism is and always will be completely fucked up. Long before I could express how.