Service related issue

I worked in an organisation and i had dispute with them. They called me to their office on 19th of June and asked me to resign. We had a discussion and finally agreed that they will pay me salary till 31st of August and told me you will get your money calculated till 31st of August after you will give hand over company's asset. On 24th of June i went to give handover and asked them when i will get my money for which they said you will get it on monthly basis and August salary you will get in full and final. I spoke to them and told them on 19th you had given me salary acceptance and relieved me on sam day then why monthly payments and if you want to give monthly payment then give me accepted resignation of 31st of August. They are not ready for it so if i will get accepted resignation document which says accepted and relieved on same day but they will provide relieving letter with relieving date 31st of August. HR told me relieving day and last working necessarily not to be same. Kindly guide how i can deal with it as if will give accepted resignation and relieving letter to a company then it wil have different dates and company will treat me fraud.