Company Beholding relieving colleterals

I was working in a digital learning app as a regional manager, From July company holds the salary the reason they said the clients (our client's Schools) have not yet shared the student's data. that's something sole discretion of the schools we couldn't enforce. I was really upset without any notice they suddenly hold my salary I decide to quit the job. I requested for resignation on 17th august and clearly mentioned my last working day will be 31st august 2022(in my offer letter there was no clause for a notice period so I gave two-week notice as a formality ) Still the company not giving the acceptance of relieving and beholding my relieving collaterals like July and August salary relieving letter etc. they sent an e-mail just like below. Dear Harikrishnan, Your relieving date was not agreed upon as 31st August 2022. As discussed and intimated, your last date was supposed to be the day 1. when you collect the student data of all the schools you had signed up 2. introduction of the schools to Mr. X is done As you have NOT completed both of the above, we are withholding the relieving collaterals. Thanks, they send Mr. X on 19.08.2022 only I introduced him to clients but still company beholding my relieving collaterals because all schools I signed not share students database, its something beyond my hand now I am getting offers from some companies but because of this I couldn't join please help me Yours faithful Hari Krishnan