Been there.
I got refused letter too last year at June. Due to lack of Job description. In my case they were asking Employment letter which my HR did provided one, but the one HR provided wasn't the one CIC want. So you have to figure out what format or information CIC wants to know and draft something for it. I will suggest you just find someone(lawyer or consultant) who is capable of review your documents and apply again.
They don't accpet any dispute and not open to review your case, if it's refused, there is no other way but to reapply.
So, good luck and don't waste time thinking about saving this case which i tried but failed.
Wish you good luck man.