Can someone enlight me

Good day!please can someone please enlight me on how and what to do to solve this problem.
The company i am working with was treating to cancel my visa all because i log a complain about the work i am doing which is not what i apply for. it happen that on january 2011 i got an offer as a supervisor on my field which is mechanical engineer with this company from nigeria and when i came down i was turn to mechanic which is not what am here to do,i have been doing that since i came in,so it happen again on the 25th of april that the company call me that they are changing my duty that i have to work as a crusher operator in one dusty area of duhail but due to the fact that i dont want to complain i went there and i started working but it happen that on the 30th of april when the dust was too much for me to bear i mean i was not feeling fine i started vomitting and having all kind of abnormal feeling then i went to the company that i can't continue the work again because i was not feeling fine and the company said they will cancel me because i refuse to work