Here I always thought that Mrs. was never used unless the person told you

Here I always thought that Mrs. was never used unless the person told you to use that or one is 110% sure they are married, though the latter situation is less commonly used as it often leads people to believe that a married couple shares the same last name. Teaching kids that married women go by Mrs. without mentioning that it is that person's choice is problematic.

Do the people at your office generally address you by your last name? I get that the West Coast is more casual, but standard practice here seems to be to address everyone by their preferred first name unless it's a legal document. There have been times when I haven't learned a person's surname until much later. Even the CEO is referred to by their first name. This also helps when one doesn't know a person's pronouns.