Tech Mahindra — tech mahindra joining

Tech mahindra recruited 8000 candidates all over india and provided them with loi back in 2016. Now after a year they are telling recruits that before joining they will have to give another test and they are stalling offer letters. Since company is a huge firm students are afraid to do any thing. Students made hundred of tweets thousands of mails to company. But company is not responding.
Company replied that they can do this as it is their business requirement. Since students were selected in this company they were not allowed to sit in any other company. Hence please find a solution to this situation