Airtel — Rs.30 debit from my main balance after did recharge of Rs.49

Dear sir, i did recharge of my airtel no [protected] of Rs.49. on 16 Dec 2020. after recharge done Airtel deduct of Rs.30 from my main balance. i called to customer care number they told me it is 2 month subscription charge for hello tune... last month i did recharge with unlimited plane and this month i recharge with Rs. 49 that's why you deduct my money ..why should i pay for 2 month subscription ...i have no information about this subscription is chargeable ...please credit back my money or i will port my number with other operator