job relieving letter

hello sir, I am in a peculiar situation. i am selected as a "intern" for about 3 months(from may 2014 onwards) in a small PVT.LTD company. they issued me a offer letter stating that i) they give a stipend of 8000 per month II) i need to serve for atleast 3 months; On succesfully completion they may observe me as a regular employee. i signed that offer letter and sent to them and i joined there. After 1 month,the issue is "i need to quit that internship and need to go for higher education". when i said it to my boss. he is asking me to pay 20000 rs for 1 month training and also to loose the 1 month stipend of 8000(i.e for may). my question is 1. i am ready to lose the stipend for indirect charges occured to the company for training. 2. on what base he is asking me to pay 20000 rs. i never signed any agrement papers or bond papers regarding this. 3. even in the "offer letter" also, they didn't mention about this and didn't mention about what to do or pay if one quits in the middle of training of 3 months. 4.for my other colleagues, he is paying 5400 only and he is saying that PF and ESI cuttings. can PF/ESi be deductable from stipend.? boss is insisting me to pay 20000. otherwise he is not going to relieve me.And above that he says that he will forward a letter to the college where i am going to puruse my higher education.. my strenghts: 1. i didn't taken any money during my presence in the organisation. 2. i didn't made any bonding with them. 3. after i signed the offer letter. they didn't given any appointment order or letter to me untill now. 4. they taken me as a "intern" not as employee and will pay only "stipend" not salary. some reasons for leaving: 1. poor infrastucture . proper training. please help me sir. how can i proceed further. Thanks & regards, srikruthi.