Robinson Hospital threatens patients for non payment although they received payment

My daughter went to Robinson Hospital with her little boy. She had to pay before he could be seen by a Doctor. She swiped her card and then tended to the boy. Now months later she is being threatened by the hospital to pay again as they cannot find payment on their system but her bank statement clearly shows payment made. They refuse to accept this as proof! How on earth do they tend to the boy and then months later demand payment again!!!! You cannot make use of this hospital unless you pay in advance.