Magicpin — Unfair trade practice on save athon offer

Magicpin has launch a offer sav a thon on 9 may 2023 in which 4 transactan has to be done with in 30 days of 25 rupees each in 4 diff. categories to get a 500 amazon voucher and I have done 3 transactions but on 10 may they have changed their T&c and mention that 100 rupees transaction has to be done to get the 500 amazon voucher but they have reversed my previous 2 transactions because they are not of 100 rupees but if they are updating their t&c then what we have done previously should be considered because according to the previous T&c i am eligible. and Now i have again done 100 rupees transaction on 16 may and the transaction got counted but today on 17 may i have done 1 more transaction in different category but ths time this transaction is not considered and when i reach out to them they told me that they have taking this offer offline. Is it fair with customers magicpin is wasting our money and making their profit this is unfair trade practice and someone should take serious action against it. One more thing that magicpin has not provided their number anywhere in case of emergency we can't reach out to them which is also very bad and unsatisfactory in terms of customer support.