Airtel - Repeatedly wrong info given by customer care executives

I have a special offer of Rs ***(*GB *G/*G) for ** days. For availing that I added Rs *** in my main account balance so that I can recharge using ****# but couldn't as there was no such option for special offers for my phone no.
I called customer care and to which he said that it can't be done by main balance and for that you have to visit the retailer as only and only he can do that. I did the same.
Now today I got to know that I can even recharge my no. for a special offer using my Airtel app. This info was not given by him that day, not even a hint. This is not the first time when the customer care executives
have given incomplete or wrong information. Kindly train your executives. I will not tolerate such nuisance afterwards.