My previous company is not providing the experience letter

I started to work as a project Trainee in one company' they said that it is for 5 months of Period after that we will make permanent employee .In the agreement It stated that it is for 5months of period and we will evaluate your performance based on that if we think it's is required to prolong as project Trainee we will increase your trianee period like that it mentioned. And I worked for 1.6 years as a trainee only I got salary through NEFT in the company name to my personal bank account. And after 1.6 years I have got another job and I put my resignation and asked them to provide the relieving letter and traineeships service document for 1.6 years. they harassed me alot in intial stages and requesting for a long time they provided me a relieving mail stating that I have been relieved from.the company services with my last working day. but now they are not giving me that 1.6 years service document for me.and I need to submit this service document proof in my new company. I don't know what to do now. we are very poor family to fight against that rich people. now I had that agreement photocopy , bank statements, and relieving mail from them. And I have the voice call proofs that they are saying we have given the relieving letter go out like that.or other wise work here for 2.5 years we will give you the experience after that ..please help me out