Unhelpful banker, currency manipulation on my international purchase

I was a victim of “currency manipulation “ by Nedbank. For the first time ever since I’ve been buying from Micheal kors online for years, an incorrect amount was deducted from my credit card. My so called banker won’t resolve it or refer it to the correct person to investigate. She is refering me to Micheal kors, eventhough I told her it’s not a Micheal kors problem because their invoice reflects the amount I saw in my cart at checkout, problem is on my nedbank statement!!! She is also playing the currency exchange card but my question is”SINCE WHEN????” Since when is that an issue because it’s never been? Why suddenly??! This has left a bad taste in my mouth 🚮🙄