Airtel — airtel 399 offer is not working

Address:	Hyderabad, Andhra Pradesh, 500084
Website:	www.airtel.in

I have recharged my airtel number with 399 offer which is for 84 days unlimited calls and 1gb internet /day for 84 days on 31st aug'17. But i got a message that it is valid for 28 days till 27sep'17 only after recharging, what is this? What should i do to get my offer completely. I request to get my plan for what i hv done the recharge for. Ihave attached the offer given in the app and the message i recieved after recharging, tell me what should i do. Will i get my money back or will i get my complete offer as told in the description.??