Payment of account

Practice calls numerously of outstanding account which was submitted on the 8 December 2016 for service dated 3 October 2016 and submitted with batch 216917. Called call centre various time who did want to assist with the query, every time another story. Advise to send an email which was not answered and when calling to speak to a manager I was told that the Manager was fired. This is dragging since December 2016 and nobody can look into the matter