Empty promises

I have been needing my invoice for work. I was debited on the 1st of the month, and I usually get it on the 2nd. However when it didn't arrive, I contacted them. I have spoken to 6 different agents and each time I was told that the matter was escalated and I get given a time frame to wait. Some say the next day, others within 48 hours, and last week friday I was even told 72 business hours. It is now the 17th (16 days after payment was made) and I still have not received my invoice or any recompense for the time spent following up on my query. I have been patient long enough.