just wait and relax. In some companies, HR staff will finish reference and background check first, and then they can give your offer. Before that, they won't tell you anything about the offer. BTW, don't call HR people again. I know a lot of HR people are very mean to foreigners since they don't want them to make troubles in the future about some immigration stuff. Sometimes, they will try to pursuade the department manager to change another person. Hehe, sorry if I scare you.