National Highways Authority Of India [NHAI] — Hdfc fastag issue with server down

On 29 April 2021, I traveled from Chennai to Madurai. I had inr 1000+ in hdfc fastag wallet but then on each toll gate I was told no balance and I ended up paying twice the toll amount. On calling hdfc fastag customer care, i was asked to wait for 5 to 10 min as the server were down but then nothing changed. Finally i ended by paying extra inr 700+. I raised complaint with them and today 1 May 2021, I do see some more debit in my wallet stating the transaction date as 29 April 2021. Finally I am paying 3rd time for using toll.