Standard's sudden denial was inexplicable

I was placed on disability by my doctor with a diagnosis of Cognitive Impairment (supported by both a neurologist and a neuropsychologist) which severely affects my ability to do my job. I received regular STD payments from The Standard from mid-February until mid-August at which time I was informed that a medical review had been conducted and further payment of my claim had been denied. During the time that I was receiving payment the representative repeatedly told me that my doctors had not faxed information to them when in fact they did, he requested reports to be completed by my doctors over and over (the same forms) and each time I had to pay my doctor by the page for these reports. I ended up sending the completed reports to them myself because the representative denied receiving them and I wanted proof via email. My condition did not improve (and in fact, will not) during the time that they were paying my claim, so the sudden denial was inexplicable. I am being sent a denial letter after which I can request and review my file, and then request an appeal. I have no confidence that completing this exercise will make any difference as I have read that this company is in the business of denying claims, I am beyond dejected.