State Bank Of India [SBI] — excess amount debited

Address:

600063

My vehicle Id registered for SBI fastag account is 459578 passed through Vanagaram toll plaza yesterday at around 1.47 PM and an amount of Rs 40/- was debited from my fastag account. I returned through the same toll plaza around 5.00 PM yesterday itself (invariably it is a return trip the same day) and again Rs 40/- has been debited instead of Rs 20/-.
Not sure why fastag people are cheating customers like this.
Request you to arrange for refunding the excess amount debited to my account and ensure that the same incident is not repeated