unpaid account

I have an unpaid account with Target, they failed to claim with correct codes with my medical aid. After my inquiry with my medical aid to try and establish the cause of non pay, I was advised that the lab did not use applicable codes hence they were unpaid. I informed with them that I had benefits they must reclaim with correct codes but they did not. they decided to hand me over to collection for accounts. I called them again to find out if they've been paid, they said no payment was received. I verified with my medical aid again, according their records Target lab did not reclaim with correct codes. I called again on Friday morning and spoke to Isaac, I wanted to find out how best could we resolve this problem, he said he doesn't know what to do with my problem. I requested to speak to a manager, he said the manager was out. I called again in the afternoon he said the manager was out all day but he's got my details he'll ensure the manager gets back to me. Target lab have not been cooperative since day one their staff are not reliable, if they say they are going to call you back, it never happens as per my continuous experience with them try to sort out this matter. Isaac claims the Doctor did not put specific codes on my form, according to understanding if there was insufficient information in my form I should have been informed timeously so that I could have rectified it with my Doctor. According to my medical aid as a patient I'm unable to rectify claiming codes only the Lab is in a position to reclaim with correct codes. Right now they have handed me over to collection and they do not want to rectify the mistake they made. I have tried to follow up with them several times to check if they are paid but I have not had any luck with their cooperation. I do not mind paying for what I rightfully owe but it would not be fair to pay for other people's incompetence and mistakes.