Jhankins

I just bought a 09 f150 king ranch and it's got 70000 miles on it and when I was test driving it drove fine so I bought it then I came back in the next day to pick it up and the battery was dead so they replaced the battery and I started to drive home the the wrench light came on and my speedo quit working fuel gauge said empty and traction control light was blinking and tranny was shifting hard and check engine light came on. So I turned around and went to autozone to check the code and it says lost communication with the pcm. Was there anything they were supposed to do after they changed the battery. Cause they have had the truck for three days saying "they are working on it" and I'm getting restless. And that same night I pulled the fuse for the pcm and switched it with another and it drove fine all day till I started it the next morning?? Any ideas??