Unauthorized Account Transactions Capitec

I've been a valid customer to Capitec since 2012. And have had a pleasant experience since I started until today. An unauthorized transaction went off from my account. Usually internet transactions go through my phone for approval. And that's the security system I've known Capitec for. Until today. Now I'm being told by the bank to pay additional money for the investigation of how the money was lost from my account. I pay and entrust capitec to protect my money. Why must I now pay to investigate how money was lost from my account without my approval and under capitec nose.

I need to get my money back. I'm not willing to pay for a service I've never signed up for. Please sort this out. I'll need to take further steps if it's not sorted out. How will I trust my money's protection in the future with this bank if this continues. This is very disappointing.