Fastag — hdfc bank fastag no updates for new fastag application on mail or mobile.

I have applied fastag on 29th Nov 2019. unfortunately the HDFC website gave an error after debiting my payment. using my credit card, I have got the SMS stating my payment was successful. But my page session was ended and I couldn't get any confirmation regarding my transaction. I called the HDFC credit card department, they said the payment was made successful but there was no answer from fastag. I didn't get any response from them. I tried calling customer care several times and it's always busy. Don't know how to proceed. I oblige you to kindly provide assistance in this matter.