Airtel — 399 plan false advertisement

As soon as i inserted my airtel sim in my new 4g phone, airtel sent 2 messages advertising about their 399 plan valid for 84 days.
Same was checked and verified on their website by logging in.

2 days later as i login to actually recharge the plan, they do not have that plan available anymore. Instead, they have a 399 plan valid for only 28 days available for my number, while other airtel numbers on my account have that plan available.

Clear case of false advertisement. If you are denying a certain service to a customer after advertising it to them specifically.