Upvote:2
Your question mentions the fact that you are expecting to get an invoice before the flight. There is a very good reason that's not possible in that an invoice is supposed to be issued only for services that have already been rendered. A document issued before that is called a "pro-forma invoice" and typically not enough to claim reimburs*m*nt (perhaps this is what you call a "receipt"?)
I am surprised you found a travel agent that would issue a proper invoice before the trip, my experience is that I always get an invoice (by email) from the travel agent after I completed the trip, even though my credit card was charged immediately after I booked. And offering this type of service is exactly why my employer pays a travel agent in the first place.