Anything that needs to be read over the phone should probably be written out using something like the NATO phonetic alphabet, split into smaller chunks if needed: "The code? It's kilo eight niner; one three mike; delta echo lima."
In other words, asking a customer/consumer to be able to recite something in phonetics is not realistic in most cases.
Fortunately the code already takes this into consideration and removes ambiguous characters.
I also ask them to check my readback of key information they have given me and vice-versa; usually that works well.