I just had an incompetent Arborist prune my Green Giant. For some unknown reason he cut 4 branches totally off leaving a huge bald spot front and center of my row a arborvitaes. They claim it will grow back by next year, but I do not believe this for a minute. See the picture of the damage they did after I have been growing these for 7 years. And would anyone out there know why a "professional" would do this to a tree? I am just furious and cannot wrap my head around it. I think it was just plain malicious.
Those branches will not regrow - growth buds on these trees are at the tips of branches, or along the green branches, but not on the trunk or on old wood. Although not exactly the same situation, the answer contained in this thread https://ask.extension.org/questions/404019 should be useful to you.
I don't know why they saw fit to remove those branches, perhaps they broke them by accident initially, but you are justified in being cross about it, I'd be absolutely furious - the best you can hope for is the surrounding green branches will eventually bush out more and cover the bare part of the trunk that is, currently, highly visible. It seems they have not provided any explanation for what they've done, but unless they can provide a good explanation (such as rot or something) I would be asking for compensation. And never using them again as well as leaving a bad review anywhere you're able to to warn other people.