Yatra.com is giving so called offer "Buy 1 get 1 offer". I booked 2 tickets from Yatra.com which has base fare Rs. 748. As per the offer, I can buy two tickets on which base fare will not be charged. So, the next day I tried to book 2 more tickets for the same flight and same date. But what I see now is that their base fare is reduced to Rs. 1 and they adjusted everything in the taxes. This looks suspicious to me. How can base fare be reduced in 1 day ?