Wimpy International review: fraudulent transaction

I am a South African currently working in Zambia.
I bought food on the 29 January 2020 at 07:02 to the amount of 300 Kwacha (314.16 Rand) and paid with my debit card at the speed-point.

After 2 days I realized on my bank account that an extra amount of 30 000 Kwacha (31 134.35 Rand) was deducted from my bank account from the same Wimpy merchant. Which I did not authorize.
Upon going to Wimpy Kitwe, the manager showed me a speedpoint slip and denied that the 30 0000 transaction went through on the speedpoint. Yet I have proof that the 30 000 Kwacha was inddeed debited off my account from the same merchant, and my bank also confirmed that the transaction indeed went through.

My Contact info: via email r.[protected]@senet or [protected]@icloud.com to resolve this issue.
My Zambian contact number is +[protected]

Note: I have also reported it to the fraud division at my bank in South Africa (FNB).