Airtel — trying to make money out of its customers

Address:

Pune, Maharashtra, 411006

Dear sir,

My phone number is [protected] and i've been a loyal customer of airtel since last 5-10 years using airtel broadband at home as well. I have a main balance of almost 1500rs but i'm unable to use that balance for recharging any packs like 399 plan. Where am i supposed to this main balance then if i can't use it for recharging basic packs that's appearing in myairtel app and also in 121 code. This is highest level of cheating by airtel.