Interest charged without justification

I have always ensured that I pay the full amount due on my credit card before the due date. The statements I have received have always reflected as such. However when reviewing the transaction history strangely the transaction history doesnt match the statement and interest has been charged. After querying this the statement in question has strangely disappeared from the Discovery App.

Discovery have eventually responded with an anonymous email which doesnt resolve anything. Mistakes can be made but when the issues is raised surely we can expect that someone competetent will investigate. Clearly this is not the case with Discovery Bank.