ITCBA destroying Bonitas business reputation

I cancelled my med aid policy with Bonitas and moved to a different fund through my company associate. Normally all Bonitas funds are deducted from my salary hence I expected any debt owed prior to closure to just be deducted from my salary. When I cancelled I wasnt informed about an outstanding debt. In December I got a call from ITC to inform me about my outstanding debt. I then paid it on the day all the monies owed to Bonitas and recieved the email with the proof of all outstanding debt being paid. ITC however continues to harass me daily stating I owe them R500 odd rand admin fee and then I am sent threatening messages telling me I need to pay R99 by the weekend as they havent recieved payment when I got confirmation from Bonitas. If I paid Bonitas why am I being asked to pay an additional amount that varies directly to ITC. I have no business dealings with them hence I shouldnt be paying them. I hold Bonitas accountable for their 3rd party behaviour.