HDFC Fastag — Unable to contact HDFC FASTag customer care

I have an HDFC FASTag which seems to be damaged and needs to be replaced, however, the only way to get it done is to call the HDFC FASTag customer care number[protected]. I have been calling this number for past 3 days but nobody answers the call and it gets disconnected after a long hold music for a few mins. This is really frustrating and not expected from bank like HDFC.