"o" before recent phone number, what does it mean I just realized I got some recent contacts who have an "o" before their phone numbers when I'm adding a recipient after writting a text message, what does it mean?

I'm sure it's the letter "o" and not a zero because it appears when I search for "o" when adding a recipient. And it doesn't appear as capital letter before the number, it appears like "o961231234" and those contacts are not on my list, but they do appear as recent contacts.

Please, I'd really appreciate if somebody could answer this
The letter 'O' before a telephone number is for OFFICE.
'F' for FAX