The Pentagon can I should say no but if they think it’s needed they shouldn’t expect a private company to foot the bill.
From what I understand, Musk took it upon himself to activate StarLink in Ukraine at the request of Ukrainian Vice Prime Minister Mykhailo Fedorov. As far as I know the Pentagon/Defense Department had no active role in it being activated. If he wants to shut it down, that's fine, but the U.S. taxpayers shouldn't foot the bill for it to continue. Let Ukraine use some of those billions they've gotten from Congress, and haven't had to account for.