Airtel — unable to recharge with my main balance

I have 220.00 rs.in my main balance but still i cant activate offers with my main balance through my airtel app. Why do i spent money to recharge, as customer care said me to do, while i am having sufficient balance as my main balance. Please give some alternative as my airtel app is showing only two options that are net banking and pay with cards like debit or credit card. Though my airtel app balance is nil but i have much more money in my main balance than the amount of recharge as shown in offer i. E. Of 199