HappyEasyGo — wrong charges taken for flight booking

Trip id : xxxxxx[protected]

I have requested to book a ticket through happyeasygo from bengaluru to varanasi for dated 05-dec-2020 and also requested to utilize my credit shell amount of 11739/- for booking.
Before ticket confirmation, i have paid an additional 1500/- rs as requested by happyeasygo, but the actual fare after ticket confirmation is showing 10452/- inr. Since the actual fare of flight booking is lesser than my credit shell, my credit shell is not completely utilized on top of it happyeasygo has charged rs. 1500/- which they are not able to justify and are not ready to return also.