Employers, managers, supervisors all misbehave before and after resignation

I am working in private IT company as a Consultant now. I have one year of experience in this company. Employers, managers, supervisors all used to misbehave with me since 6 months. Before 6 months my HR forced me to work after company working hours. I have voice recording of this conversation because lots of worker told me that HR used to misbehave with workers during this type of mattings. Than I decided to complete 1 year in this company. So I decide to resign through Mail because of I have anxiety and depression problem and I have decided to shift my home town for my further study and My class will start on 17 July at my home town . I have resign on 12 May than after I gave them 2 reminder mail also. They excepted my resignation on 18 May. I mentioned my Last working day (date = 12 July) after 2 months of resignation and reason of resignation (I have decided to shift my home town for my further study and My class will start on 17 July at my home town). but they are not providing me my last working date. Also I went to HR department, First they abandoned my phone with me in HR mitting Rome. They told me that You will get all your documents(Experience latter, FNF salary, and form 16A) after 90 to 120 days after your last date of company. And they told me that they will stop my salary during my notice period because of security issues. I do not know what should I do now?