according to many it IS a lack of tznius to call people of the opposite gendeer by their first names.
for women introducing oneself as Miss/Mrs…. automatically puts up a barrier between the coworkers a barrier you want there. If you can’t start asking everyone to address you with a title… address them mr,miss,mrs so you build that barrier…
bhatzlacha!
also you may want to ask a sheila.. ASK= Always Seek Kedusha (Rav Yehuda Oelbaums abbreviation)