For example, when paying a bill I have to give out my credit card number. Do you just rattle it off as fast as you can read them, or do you wait for some signal that they’re ready for for the next batch?

I read off 3 numbers at a time, clearly, and sometimes we get into a cadence of me saying, “457…” then she’ll say, “K,” as a signal she’s ready for the next 3.
Most often, though, I listen for 3 taps on the key board on the other end, then read the next 3.

I’ve worked in customer service for years, and most people don’t understand what it’s like to field a bunch of unfamiliar numbers over the phone. They don’t understand the need to speak slowly and clearly. They’re especially bad with numbers they have well memorized, like their own phone numbers. I once asked a guy for his number and he said, in a rush, ”Fourfiveeightdoubleoughtthreeseven” I was like.. 458…double ought? Oh. Country talk. Means 00. So 458–0037.