1997 Mercury Tracer Car Running Hot

Car overheated yesterday. Took it to Firestone and they replaced radiator and thermostat and flushed the system and added new coolant. Today, driving home the temp gauge shot up to just befoe the H. Stayed halfway between the middle of the gauge and H the rest of the trip. Also, the heater started blowing hot and cold air intermittently. Secondly, when I got home and looked under the hood, there weren't any leaks. I looked at the radiator and on the bottom front side about three quaters of the way down, I noticed the radiator looked used. The metal is bent on about one quarter of the radiator. Is there a way to tell if I got a used radiator installed instead of new.