Claim not paid

Hospital submitted a claim. Medical consultant thought it was a dupicate of which it was not. They decide not to pay it. It get brought to our attention , my husband goes to there walk in centre in town, he is told to hold on they will get back to him .He goes back to work forgets about it as he feels it will be sorted because it is the medical aids mistake as it was not a duplicate but an actual invoice . When my husband eventually gets feedback he gets told Medical aid will not pay because the 60 days in which to lay a complaint or queri has passed. We can not accept this as it is not a fault from our side , it was there fault why must we pay for there consultants incompetence. We have not once missed a medical aid payment I feel we are playing our part .they should play there part and pay for there mistake .Why must we pay for there mistake.