Work for this company

Q: I work as an accountant in a Saudi company, that works in the field of operation and services. The company pays the salaries of its employees from its revenues that are yielded from different projects done for the state and other companies. The competent manager in this company is Christian. The company had to take loans from one of the usurious banks to pay the salaries because the state delayed their payments. The company takes these loans (Part No. 15; Page No. 28) in return for usurious monthly interests. Being the accountant of the company, I issue checks, record the expenses and revenues in the company's books. I record the loans' interest as expenses which the company owes the bank. It should be noted that I have advised the Christian manager about this. He said that he had to take loans from the bank to pay the workers their salaries and to purchase different materials for the project and to keep the work running. It is worth mentioning that both the general manager and the head and owner of the company who works as a counsel in the Saudi American Bank, know all this. When any of our brothers tell the owner of the company about the usurious loans, he would say that the competent manager did nothing against the regulations. I opposed this vehemently and threatened to tender my resignation. But as you know the company is responsible for my residence. They told me that they would not transfer me to another guarantor to prevent me to work in another place in the country. They told me they would issue me a final exit visa to go back to my country. You know the worldly and religious benefit I get by staying in this country, thanks to Allah's Grace. Allah (Exalted and Praised be He) blessed us with guidance in this country; all praise be to Him. What should I do? Should I continue working in this company and keep advising them despite my refusal of their practices or tender my resignation and go back to my country in which you know its situation on worldly and religious levels?