No invoice provided

Hi

I work for an organisation who is willing to pay for my studies. I have requested a invoice and a letter with the banking details. I have been asking for this once a week since January and I am still waiting. The payment due date for First semester has passed and I'm afraid that since I have not received an invoice to pay for registration. They do not answer the phones or even the several emails I have sent to their ********** or their general email. This is such bad service. Its disgusting and unprofessional.