I'm sorry you are having problems with your vehicle. I will try to help.
I'm a full time mechanic and have been a mechanic for over 20 yrs and I work part-time here on JustAnswer to help you and others repair their own vehicles, and I get credited by your ratings.. So before leaving the site make sure and leave me a rating. You can still reply to me as many times as neeed, even after the rating.. I will need for you to be my hands and eyes since I'm not there.
So I would recommend bringing it back to the mechanic to have him fix it. he likely didn't get all the air bled out of the system. But here is how you test the system if you want to know.
1. First check the engine operating temperature. It should be able to get to at least 180 degrees if the thermostat is working correctly. Also ensure the air has been purged from the cooling system.
2. If the engine temperature is correct, then check the inlet and outlet temperature of the heater lines at the heater core. If the inlet feels hot, but the outlet is cool, suspect a plugged heater core.
3. If there does not appear to be much of a difference in temperature between the inlet and outlet, remove the heater hoses from the core and put them into a container. Start the engine and check coolant flow. There should be good flow like a garden hose. If the flow is weak, check the water pump and engine coolant passages.
4. If all is ok, but the temperature still won't get hot, check the temperature blend door actuator operation.
I strive to provide 5 star service. If I have satisfactorily answered your question please rate it as such and hit submit. Doing so is the only way I get compensated for my time. Also it doesn't close the discussion so we will still be able to communicate if there are further questions.