Over-billing due to lack of communication- Refund?

In 2013 I app**** for medical aid for my mom with me paying for it. Everyone was so helpful and quick to assist. The beginning of this month a R1694 was deducted from my account in addition to the normal payment. i called Bonitas and was told that it was because my mom did not complete the Income verification documents and was automatically put in the highest income bracket. My mom did not receive ANY communication regarding Income verification and one of your call centre agents confirmed that nothing was sent. I was then told to complete the income verification so that the case cold be reviewed. I forwarded the relevant documents where Bonitas could see that my mom is STILL a pensioner and has not decreased in age. The income bracket was then updated to the correct one but NO REFUIND without a valid reason? I believe this to be unfair practice and would like assistance in this regard please.