Double deduction of loan for another family member

On the 04 February 2022 I made a R800 loan from Takealoan. However on 28 February they twice deducted R1111.50

My sister also has a loan with them and has unfortunately failed to pay them this month.

He first apologised for the error and said its the first time they have experienced this, and that my money will be refunded. A few minutes later he asked if I know Elriza and I said yes. .

He is now penalising me because she failed to pay them this month and only says I need to speak to my sister about my refund. My contract is not with my sister. In fact on the day he made me approve the debicheck 4 times because he said its not showing on his side.