Right now is the worst time to think about the legalities of your agreement with your current video production company. This should have been an element of your understanding from the get go … particularly whether the video content you have is licensed from the video company or is considered work for hire. I'll assume that your company engaged these folks under a work for hire contract … i.e. that you and your company own all rights to the material you paid to have done. This is common but not universal.
If the content you have is considered work for hire; you can pretty much fire 'em and keep and maintain the content they've produced for you and allow others to use that content without further compensation.
If not, then you have a judgment to make … how important is the future use of the creative these folks have created over time? I'll use a company that makes fishing lures as an example and put it in the context of an annual catalog using still photography. If the company wanted to fire the guy who had done their photo work they likely lose the cost of the four-color separations of the company's head quarters but if the company is just making catalog sheets only of the new products for the next year (adding to the old catalog) then the plan would call for new photos of the factory, etc. over a two-year period. You'd have that extra cost for the next catalog but if the new catalog is 90 percent new content … who cares they have all that old stuff. If on the other hand, the 'new' catalog is 90 percent old content you need to negotiate now and fire later.
Notably in video there are other concerns with commercial work including details such as actor releases, location releases, etc. that are a necessity in today's litigious world. If your company has been requiring and keeping these documents for the content created on your behalf, you're ahead of the game. If the video production company was keeping that information, well hope they don't have a fire because you're vulnerable if they do; especially you don't have a comprehensive contract for services with the video production company.
Still, generally speaking, these folks are eithier servicing your business effectively … or they are not. If they are not, you could consider firing them.
But before you do, please consider that failed communications in business dealings are often due to misunderstandings by both parties. Said differently, ask your self if possibily your management of the relationship is the cause of the decline in the quality of work you're receiving. Remember, feelings of distrust are contageous.
Still, if you do decide to fire them, at least make sure you have an agreeable understanding, preferably in writing, that addresses these issues with your new video production company.