*********** staff and empty deliveries

I usually get my invoice between the 12th to the 15th. My employer has been waiting for me to submit May 21 invoice to get reimbursed. Today is the 21st and after numerous calls and being sent from pillar to post, I still have not received my invoice for May21. 3x I have been incorrectly sent April21 invoice and I was even told someone sent my query to the wrong department. The incompetence is beyond me. My query is forever escalated with no resolution. My employer has not reimbursed me and left disorganized for not claiming telephone.