CGI interview 12th Nov

Got a call for CGI interview for 12th Nov drive. Is it compulsory to accept the offer? Can I decline it for now? Since I have applied without any reference so I am thinking to decline this time as attempting now would make me invalid for next few months.I have again taken the test on 6th Nov with the same registered id and hope to get better score than what I secured earlier. Is it appropriate to decline now the drive letter and apply with the new score for CGI