Airtel — misleading airtel package

Address:

711109

My airtel number is [protected]. On 27th august 2018 i had done a recharge worth rupees 99. As per the information provided by airtel, the recharge was supposed to last for 28 days. But i recieved a message informing me that the package is valid only till 5th of septemper 2018. I searched online to check if the plan has changed in the recent past but i realised that it hasn't. I want airtel to kindly look into this matter asap.