I think what you need to ask for is an official offer of employment, in writing, laying out your start date, responsibilities, pay, etc (knowing, of course that it's not a contract of employment but verification). The company you're tentatively working for may be different (and also I'm no expert on employment issues), but the one I work for does this for everyone they verbally offer a job to. What I would do is put my request in writing; reference the discussions you've had about employment and then ask politely for the written offer. Definitely don't express frustration with the way they do things, because you might look uncooperative. If they say no, then you know it's time to move on and find a company where you won't be jerked around.