App and photo editor
It depends on the context of the call. If the system is asking for verification purposes, then surely it can determine if his entry is match. But if it's asking for new data, then you're right, there is no way for the system to know which letter he meant. That's why I'm wondering the automated system was actually asking him to speak his entry into the phone; this is very common now. This is the only method of sending letters through a telephone call (without speaking).
Originally Posted by Stevie No-Wonder
Technically, a machine would be able to receive letters if the entry is in old school texting format (2=1, 22=b, 222=c, etc). But as far as I know, this is not a method that is in practice. If so, I'm certain the automated person would have gave him instructions to enter it like that.