non-payment of salary

Dear Sir/Madam, I "Jayashree Samantaray" was working as "computer faculty" in "SMART IQ" institute. I had decided to quit the institute as the management was not able to pay my expected salary. And finally, left the institute on December 27,2014. When i joined that institute on April 19,2014, at that time the management commited to pay my expected salary i.e 9000/p.m- as i was drawing 8000/-p.m in my previous institute within 2 to 3 months of joining. As i had came to this institute in my friend's reference, i compromised with myself and agreed to take 4,500/- p.m. After 4 months, when i said that is is not possible to continue with this much of money, then the institute gave me 5,500/-p.m. and promised me to give me my expected salary. But on December 20,2014 the management told that it was unable to pay my expected salary. So, i decided to quit the institute with 20 days notice period. They had not given me the "JOINING LETTER" . Still i was ready to give them 20 days notice period. On December 21,2014 i gave my "RESIGNATION LETTER" to them. But till now, the institute did not give me the "LAST MONTH'S SALARY' and one copy of my "RESIGNATION LETTER" . Now, i am not expecting that they will give me the "EXPERIENCE CERTIFICATE". On December 23,2014 when i told that i will take the help of police then he replied me to give complain against me also. My question is that "how can i get my last month's salary " ?