What is the ruling on working as an accountant for "Western Union" which offers interest-based loans, and is it obligatory to leave this job?

It is permissible to work and cooperate with entities whose predominant activity is lawful, even if it includes some prohibited activities, provided that the worker does not directly engage in the unlawful act, and that the nature of his work does not involve direct assistance in the unlawful act. However, if the questioner's work in the company is limited to permissible financial transfers and has no relation to usurious loans, then there is no harm in it for him. Otherwise, working there would be forbidden for him, and he would be obliged to leave it, unless he is in dire necessity and cannot find a permissible source for his essential expenses, in which case he may continue until he finds a permissible alternative. A Muslim should trust that abandoning the unlawful for the sake of Allah's pleasure will bring a better compensation.