I developed safe32 for this reason.

https://github.com/kstenerud/safe-encoding/blob/master/safe3...

Notably, confusable characters are interchangeable when being ingested (although a machine encoder MUST always produce canonical output). https://github.com/kstenerud/safe-encoding/blob/master/safe3...

So a user can confuse 1 for l, 0 for o, I for l, u for v, uppercase, lowercase etc, or the agent can say any of those over the phone, and it won't matter.