Not Responding to Queries

Ive been receiving sms's from NHLS since last month demanding payment,i called them to find out what is this payment for the Lady who answered the phone told me she is going to investigate and revert cos she thinks its for the bloods that was drawn,i told her i did not draw any bloods,She never came back to me,ive sent an email early this month no one responded again,i followed up with Mr Thabo Mnisi he responded to say my Query is assigned to Henry who is on study leave by that time he will be back following week,i did follow up again to find out if Henry is back since its that week,Mr Mnisi did not respond,i just sent him another email now to follow up,they are not responding and they do not care because i have a right to know what is this money that i must pay is it for especially if i know i did not draw any bloods.