You realize they publish their HAM call signs for the station? Like its a thing, making contact with the ISS.
Contact the ISS
www.ariss.org
And I conducted an experiment. I pointed a directional antenna into space and listened to an expected radio contact on an orbiting satellite.
You can not orbit a plane, only a sphere.
Hence, I proved the earth is a sphere.
How have you proven the earth is flat, besides reposting memes you found on facebook?