National Highways Authority Of India [NHAI] — Unauthorised debit on my fastag prepaid account

I had not even moved my car from its parking on April 01, 2021 but still my fast tag was debited as under:

Dear Customer,
Your FasTag A/c has been debited for Rs. 20 for transaction by Vehicle KA50P2311 at Toll Plaza 1 @ Km 14+825 on[protected]T19:45:00. Balance amount in the A/c is Rs. 326.5 - HDFC Bank Ltd.
Warm regards,
HDFC Bank
Bank aapki mutthi mein... Bank at your fingertips.
Request you to please check for wrong usage of my fast tag pre paid account