Milk+dressings for tubes for Prem babies not covered by Hospital Plan

Dear Sir/Madam

I'm having trouble paying for hospital bills while I have a hospital plan with Momentum. My twins were born in March and now Mediclinic is charging me for milk+dressings+multivitamins etc prescribed by the doctor to keep the babies alive. According to Mediclinic I'm liable for the account and Momentum says that these items are not part of the prescribed PMB list so they won't be paying for it. Mediclinic says they have an arrangement with Momentum and sometimes the milk etc gets covered from Momentum and other times not. I don't understand how a medical aid can justify milk, dressings for the tubes, vitamins for growth (while there were codes authorised for growth issues), etc isn't covered by the hospital plan and ofcourse the prescribed PMB list. Unsure who I should go to, as the Momentum Agents aren't even trying to help