I have reached my two year disability and i have been approved for long term disability. They want me to do a cognitive functional assessment through there doctors. Can I refuse or can I pick my own doctor as there doctor is working for them.

Typically, its in your best interest to comply. You can ask if you can pick your own assessor but generally the insurer does have the right to choose their own assessor. You can read more about this on https://stlawyers.ca/disability-law/independent-medical-examination/
Regardless, if the insurer tries to use this assessment against you, we can help. Please give us a call or email if you have any further questions or concerns.