Duplicated Charges on my account

So disappointed with Nedbank service. On 26/09/2019 they charged me twice for Lotto transaction (R2.20 x 2). I called call centre ***, and the lady i spoke to told me to go to the branch to query it, but i will also be charged a dispute fee. I don't understand how can i be charged a dispute fee for a bank's mistake. Does that mean Nedbank can do as they please on my account and i cannot query what is happening because they will charge me dispute fee? It is not my fault that they debited charges twice, why must i be responsible for dispute fee payment. All i want is to be paid back the duplicated charges. This is ****************. It's is not about the amount of the charges, but it is about bank ethics.