I find it strange you doctor started with colonoscopy rather than endoscopy. You want to have endoscopy done to check for gastritis, helico bacteria, hernia and others, PH manomentery test done to see if indeed you are refluxing and measure if you have week oesophageal valve and few other things.
if pantoprazole is not giving you relief then you can true another type, maybe like nexium, dwxilant, rabeprazole and pantoprazole, try to find a way if possible to manage your symptom without over reliance on medication if possible. also PPI take about 5-14 days to work and some even longer.
You could have gastritis or helico bacteria that is causing this reflux.