I am not reading through the responses yet. I want you simply to ask yourself how important this job is to you. If you really want it, then PLEASE be a team player and be called by your first name. There was NO such thing as last names centuries ago, when we were more formal, and no one seemed to be concerned that it was a problem. If you insist on the formality that some people might advise you to do, claiming halachic or tzniusdig issues, (wrongly, in my humble opinion), then you will alienate everyone in your office and create an atmosphere of “I’m better than you are.” You will never comfortably hold on to a job with that type of a perceived attitude, people don’t like to feel you hold yourself higher.
If this were a more formal office, then you would be correct to expect the additional respect of being called Miss/Mrs. Whatever. But that is not the case in this office or in MOST offices today, so stop worrying so much about it, be called Sora, Rivka,Rochel, Leah, or whatever your name is, in the spirit in which EVERYONE is referred to by their given names, or do not take the job if it will bother you so much.
To be candid, most jobs will expect you to be a little more easygoing in this matter, so don’t be put off by that. Don’t compromise halachic issues in the office, like kashrus (when everyone is going out to the local deli or bar after work), or tznius issues (keep the men at a clear boundary), but your name is not one of those issues, unless someone is referring to you as “Honey” or “Sweetheart,” in which case you could gently say, My name is “Ploni.”