DDI or DID? Which is correct?

Do you know, when people send email, they attach their signature at the bottom of every email… and one of the things they put there is their phone number?

Yeah, you know what I’m referring to.

Now, for many of these signatures, you will notice that one of them is the direct number to call to reach them. They usually use an acronym for it.

So… which is correct? DDI or DID?

Well, here are my findings:
DDI stands for Direct Dialing In,
DID stands for Direct Inward Dialing.

Technically, both are accurate and correct, although the more frequently used is “DDI”.

Nope, it’s not a misssspelling.