Airtel - Incorrect data roaming charge

I had traveled to Vietnam for * days with family. My wife and daughter phone is part of family plan. My wife always have data roaming turned ON as the data does not work in other local cities. My daughter never had dataroaming turned on.
During overseas trip, both received msg about dataroaming, the msg was not clear to say that you will be charged. Misleading msg has statements like "roam freely without fear of bill shock", "if usage exceeds Rs.*** you will automatically get free ***mb data, free calls"..etc etc. it was just not precise to say that you will be charged Rs.*** on daily basis.
My daughter, when data roaming was off, still received this msg. What does airtel expect the customer to do ?, when this was not even requested.
My Wife, was also clue less looking at this msg, just read as something free everyday.
We just did not call or place a request to get data roaming, but data gets used without our knowledge by watsapp etc and we get to shocking bill of **K after the trip.
*. Why Airtel sending data roaming details to ********** when there was no request of any form made, and just started to charge.
*. Why Airtel did not get confirmation from the customer ********** who always has data roaming turned ON un-intentionally all the time, by just sending and unclear msg and started to charge.
Why Airel, a huge company does not have a process to get customer confirmation on dataroaming, by asking customer to reply with "* - agree", "*-disagree", "*-call me for clarification". What they did is taking undue advantage on people who travel and make tons of money from ignorant customers. This is just an illegal business model they have in place, not sure how legal system is allowing this model.
Customer service is not even taking this as complaint, took time to convince but eventually did not get complaint number back. Not sure if she even recorded a complaint for me.
Hope Airtel can sort my issue.