Air conditioner issue

I bought a refill from advanced auto and the tech helped me, the meter read low a little so we filled the low end up until it was at the correct level, and it felt colder in the car, so success. Until a couple miles later when it was blowing and the cold air left completely, but still blew hot air. At the same time the car would idle normal and about every five seconds it would give a little rev and then idle normal, and still warm air but it came in a little and then went away again, and all this after we clearly seen it was filled to the proper level. So now I am not sure what happened, but I feel it is has to be something simple I can fix myself. Please if you have the answer or can help. Thank you for your time. Best regards, Donald Howell