I changed my batteries in the thermostat. Then reset it. Now I turned the air on. I hear the a c unit kick on. I do not feel the house temp going down. It's still hot!

Call an HVAC service tech.

You should have a unit outside the house. Is it actually running, (not just a blower fan)?

There are many reasons, one would be coolant levels, a wire loose, a internal fuse bad (LOL) I had to crawl under the house to find the one on mine.