Company refusing to give experience letter though accepted orally

It's a small company with 5 employees.I have completed 4 months training but they haven't taught all the syllabus at that 4 months period.After that I joined there itself and worked for next 4 months.Every week we have 6 working days.Sometimes they give work even on sundays.My salary is only 7k.But every month I used to get only 6k.Even if I take one day leave or if I come 1hour late to office they won't give me Salary for that day.1hour late means for example Monday if I go 15 mins late and it continues for 4 days means they won't give me one day salary.Orally they say that my designation is Frontend designer.But there is no proof for that.They haven't even issued me an ID card in the past 4 months.They don't have stable rules.Due to my mother's operation I need to resign my job immediately.So one morning I asked for my relieving orally.After few hours orally they said ok u may go.They asked me to collect my experience letter after15 days then 10 days then 2 days but not issuing