Billed incorrectly

I was billed for pediatrician for checking newborn after birth but Discovery billed me because they say the hospital must re-submit the dates. The hospital does not want to re-open account. According to discovery I was discharge on 18/07/2017 but I was discharged 19/07/2017 now they refuse to pay. Very unhappy because this bill have not been sorted out after I spend hours with them over the phone with my own airtime.