No reference letter but I do have working visa as a proof of employment

[San.Jamous]

I'm not sure if client letters work as primary evidence for employment. If you are left with no option, then you could use them. Definitely better than offer letter alone. Make sure you cover your whole experience with those letters.

Thank you so much for your reply.. I will do my best with those letters and will still talk to my ex company and hope they will provide me with the reference letter.. I just don't want to take chances with this.. I'm working so hard on it. And it would suck to fail because of something like this.