Hello Shivang,

After the JAM 2019 provisional answer key released, The candidates are given an opportunity to challenge the answers they think are wrong. This was available only in a time period specified by the conducting body. 

To Contest the Answer Key dealine was 28-02-2019, 12:00 Noon.

To check the further information you can go through with the given below link.

https://university.careers360.com/articles/jam

Good Luck!