filing resignation with valid reason but my employer rejected it

Hi! I would like to have a best advice on how will I'm going to do settle my resignation. I have already worked here for 8 months supposedly as aluminum technician as stated in my employment offer and contract.
I recently filed my resignation to my employer with a reason of not giving me my exact job stated on my contract, but he refused to received it. My employer stated that I should pay him back with all of his expenses from visa to iqama etc. I have already get an advice from our embassy and they said that all of the liabilities that he used to demand will be my agency's shoulder. I have also contacted my agency and they are willing to help whatever my employer will demand including my air fare, but it seems that my employer wouldn't want me let go. my agency have been sent an e-mail regarding of my demand but it seems they don't take it seriously. The company instead replied that I who do have problem in performing work but why dont they let me go?. this is only one of the problems I have seen for 8 months of working here including the unsafe procedure of performing work, they do not issue safety gear or equipment to keep workers in safe, holding my passport, I also asked my employer that my medical card has already expired since May 21, 2017 but it seems no actions. Poor accommodation specially the aircon thats not working well. please help me to resolve my problem. I really wanted to go back in my country and I dont want to continue working here. thanks in advance.