help with h1b transfer before starting employment

[Robias Tony]

I got a n Approval Notice for a new H1B visa (without cap) but haven't re-entered the US and haven't started my employment. A potential employer, is under the assumption that I have a valid h1b visa (without cap) and they wish to hire me.
Is it possible to file a new petition (for transferring the h1b) before starting to work for the employer that suppose to sponsor the approved h1b visa?

please help me out... thanks a lot