National Highways Authority Of India [NHAI] — Black list or low balance

When I have Rs. 96 fastag balance the Gollaprolu toll plaza id no 352048 East godavari Andhra Pradesh staff to refused to pass my vehicle no AP16BC0257 at the time of 18.32 dated[protected] and they told to me error is low balance. I need only Rs. 20 for passage of the vehicle. In the spot (18.34) I recharged the balance for Rs. 100 and next 10 seconds I got successful recharge with Rs.196 balance sms also. Even after recharge also they are not allowed my vehicle. But they objected and to want reverse my vehicle from their toll gate premises And they want 15 minutes time to passage my vehicle after successful recharge. After 18 minutes they allowed my vehicle. Why I am suffered without any negative balance.