Urgent! H1B Transfer questions

I got a job offer at the end of April and the new company started my H1B transfer process in the beginning of May. They did not file my petition until 6/5/06 due to pervailing wage (which I do not understand why H1B transfer need that). I thought I should be able to start working once they filed it since they will have a sender's copy through Fedex. But the attorney told me yesterday that I cannot start working because she has not received the petition fee receipt from USCIS yet. Is that true that I have to wait till the attory receives the receipt notice? A lot of my friend who had similar situation told me that I can start working once case is filed. I am confused now. My new boss has been pushing me to start for one and half month. I am just afraid that keep delaying my starting date will irritate him.Please help me, experts here. Is that any section in the immigration law I can show to the attorney to approve my legal status to work now? Thanks in advance.