I have worked at a reputed company for over 3 years through a job agency. My employer is the agency itself as they are the ones I have contract with, and they are compensating me for the work. Going through other threads, it looks like I need to provide letter from both the agency and the third party client to prove my job experience. However, the client will not write any letter on my behalf as I am only a contractor and that is their policy. Will I have problems in proving my job experience because of this? Is there anything I can do to strengthen my case?