Doing Procedure without checking Med. Aid funds available

Good day, I’m logging this complaint on behalf of my father who is not computer literate, and he has Parkinsons disease which prevents him from writing a letter. He is a pensioner with a small income and has medical aid membership with Bonitas medical aid. He went to Sunwardpark Netcare Hospital radiology department on 22 Jan ‘18 for a sonar. They did the procedure and his medical aid only covered R80-32 of the total bill of R 1 752.60. (Inv no: 11-119141. They did not check if there were funds available in his medical aid prior to doing the procedure. There is a sign on the wall at reception stating that they will check befor doing the procedure. I took a photo of the sign. Now they want to hold him responsible for the outstanding amount.