FD - the company are likely not allowed to file you before Std as you would then be operation off from your runway slot (nothing to do with atc but airport) and could be subject to loosing that slot
For the following season or a fine loosing historical rights and the ability to
Operate that flight at that particular time. If an aircraft is ready early first port of call will be to advise crew to ask tower to depart early (most will allow in my experience or if you have Ctot put a ready message in with tower and ask your company to speak to the CFMU PORTAL explaining your situation. Filing early is unfair to all airlines as it takes a slot from an aircraft departing on time and on more than one occasion CFMU queried and early flight plan hope this helps from the other side of the fence