Dear Samhita,
As per my understanding: If the auditor of your company (one who is giving resingation) has not filed form ADT-3 for his resingation as required to be complied with within 30 days, you can do the following;
1. As your accounts adoption date as mentioned by you is 08/09/2015 (means accounts for the year ended 31st March, 2015 have been audited by the auditor giving his resignation) you can adopt the accounts prepared and get them signed by them as they have prepared accounts after conditng their necessary audit as necessary.
2. Issue notice of AGM .
3. No need to conduct EOGM for appointment of new auditor in place of whom giving resignation.
4. Conduct AGM and pass a special resolution for the appointment of new auditor other than those retiring by providing special notice that the retiring auditor shall not be reappointed.
This being my personal opinion may differ from person to person. Other views solicited.