Airtel — Recharged twice for Airtel

Hello,
I don't have any idea how to talk to customer care for Airtel, by mistakenly I recharged twice on my phone number. I was already having the recharge of 599 and I was recharging my another Airtel no.. I kindly request Airtel to refund back my money as that another recharge of 398Rs is of no use to me and that's totally a waste of money and that's a sort of trap from Airtel side, If a person is already Unlimited recharge they should have given the options to cancel that immediately.