Relieving letter

Dear sir I have been working in a company from last 10 yrs , my designation was technical Officer to support sales , but last two yrs new state head has forced me to do sales , for that he did mental harassment of mine, suddenly one year before my company has asked sales person to resign immediately and they relieved him in one day. And all the sales pressure is came on myself After that year I have resigned and and served 2 months notice period and for one month notice I have asked them to adjust in my leaves. From resign month they have not give me salary . I am asking for relieving letter but they not give the relieving letter . From the date of resignation they have pressurised to clear the dues and then they will relieve me. My new company has holded my appointment letter for relieving letter today I am begging for my relieving letter for my previous company but they are replying me . I am salary less for previous company 2 months and for this company one month. My current company also pressurising me to provide Relieving letter. Plz help me how can I get relieving letter