Guess you haven't heard of subpoena. Until handed one by the justice department, it most certainly IS his call, same as any other citizen.
Seems he did pass on the content of that phone call that is the only evidence the hearing has. He did not have to, but libs call that not cooperating.
You realize of course, our government has no money, the total expense comes entirely from tax paying citizens pockets, yes, YOURS.
Trump WILL be in office another 4 years, how many more millions will we the people get gouged before waking up.