I don't think there is a lot you can do. For the future, get a contract in writing, read it, ask for the company policies, do your due diligence. This is even more valid once you are in Canada, make sure you know your rights and responsibilities.
No you can't sue them. Sorry to say, but it is totally within their discretion to deny you a reference letter.
Preferably they denied you via email, which means you include that communication to CIC. As a last resort, you can write your duties yourself and have it notarized.
I don't think there is a lot you can do. For the future, get a contract in writing, read it, ask for the company policies, do your due diligence. This is even more valid once you are in Canada, make sure you know your rights and responsibilities.
No you can't sue them. Sorry to say, but it is totally within their discretion to deny you a reference letter.
Preferably they denied you via email, which means you include that communication to CIC. As a last resort, you can write your duties yourself and have it notarized.