Billdesk — payment cut twice

Address:

Kamrup Metropolitan, Assam, 781122

This is sourav jyoti kalita.
I registered for a certificate exam on 31st august in nptel and the fees was paid via billdesk gateway. The first time i tried to pay, a popup came that this path is insecure. So i cancelled it and tried it again using another browser. This time it did not show the popup. But after the payment, i received two sms regarding the payment and when i checked the payment statements of my bank account, it showed two payments of 1100 to nptel on today's date. I request to look into my matter and provide me the refund for the extra payment.