The nato phonetic alphabet one cracked me up. My dude you don't need that, call center employees don't know it, just say S as in Sugar like ur grandma used to.
The nato phonetic alphabet is still useful even if the other party doesn't know it, I've used it a bunch of times on the phone to spell out my 10- letter last name. Saves quite a lot of time and energy for me vs saying "letter as in word" for each letter.
I dunno, there's a pretty good chance that the one that people spent time and effort designing to replace earlier efforts with the goal of reducing potential ambiguity and for use over noisy connections with expectation that mistakes could cost lives is probably better than what you improvise on the spot