Failing to provide invoice for the debited amount.

Telkom sent me a statement of account on the 04th of April 2022, confirming that the amount due by the 05th of May 2022 is R768.00. However, on the 30th of May 2022, Telkom debited my account for R2838.00 without a supporting invoice. I have made numerous attempts to obtain an explanation from both the Telkom store and Head Office Billing and no one can provide me with answers. I was told that there was no record of the transaction reflecting the R2838.00.