Incompetence!!

I received a statement of my account, showing that I went to my gynae on the 26th of June, and the 29th of June. I only went on the 29th. I spoke to Medihelp, who confirmed that this was an error on their side, and that they would rectify it. Then I got a call yesterday, saying that they have to wait for this correction to show on their next statement before they can do anything else. I asked when their next statement run is, and got told that there is a back log in some departments, so I couldn't get an answer. Then I get an sms this morning saying that I owe Medihelp R875! I WILL NOT PAY ANYTHING! And I will not do anything further, until they get back to me, and sort out everything on their side! It was a fault on their side, and I will not be paying for their mess ups! I hope someone reads this and gets back to me.