Airtime query

I'm having a very bad service with MTN, I received R700.00 Airtime on 06 May 2022 and after a week I only used R149.00 for data. Now my remaining Airtime has vanished, the customer service agents are taking me from pillar to post. They tell me I was rated out of bundle, others confirmed that there is no trace of where my Airtime went to. It's almost two weeks waiting for them to fix this issue. I am not happy with their service.

Now one of the agents and her manager are ignoring my calls and emails.

All I want is to get a refund for my remaining balance.