Airtel — sudden balance deduction without alert message

We have recharged with rs.28 for the internet offer on our phone on 10th dec 2017 at mid-night with validity period of 2 days i. E 13th dec 2017 but today at early morning i had on internet for the updation of one app on playstore which around 15 mb & at time my internet balance was more than 100 mb, msg pop up saying data consumed 10 mb & rs.68 was deducted from account balance which was shocking to me since i had more than 100 mb as a internet balance dear sir please take into consideration intiate the refund of rs.68

We are existing customer for more than 7 years & this was not expected from airtel. No alert message that your validity of internet has expired was recieved in my phone till now