1994 Lexus ES 300 Car is overheating after a New Radiator h

Hi
I recently had a new radiator installed on my car and now it overheats at the slightest distance driving. I can't drive on the highway anymore at 60mph or even if Im on the back roads at 45mph. I took it back to the mechanic he supposedly flush the coolant and filled it back up but I continues to do the same thing the temp gauge goes up. Also my heat won't work either now it use to before he replaced the radiator. What could be the problem?

Thanks