Shouldn't take 2 weeks to get an invoice

I used your services over 2 weeks ago and till today I have not received my invoice. The lady at the office first;y said her printout isn't working, and they will send it to me in 24hrs via email. a week went by I called the help desk told me the woman who does the invoices is at her desk and will call me back. Same as the other three calls I have made. Should it be this hard to get an invoice really? You guys are such an inconvenience. Why should I have to keep running after you for this. Why do you keep taking my details if I'm not going to get any feedback.