HDFC Bank Fastag — I paid the toll in cash and the same also debited to my fastag

I was travelling from une to Mumbai on 03.08.2020 and pid the toll in cash where as after travelling little fat i received the debit message for the same toll. when i contacted the customer care of HDFC bank theu said it can not be refunded. How can they deduct without my knowledge when i have proof that i pad in cash and the same debit is reflecting in my fastag account.