Maybe some more information is needed. How long do you continue to get water? I get water out of my spigots with everything turned off for quite a while and more pressure than I would expect. Even with the batts off so I know the pump isn't running. I think 2 things are at play; the system maintains pressure until all the water is emptied from the lines, and as things heat up during the summer - especially if you had your water heater on, pressure builds long after you shut the pump and WH off. I'll go to my camper in storage and despite emptying my lines when I put it away, I still get a little water to come out to wash my hands. Infrequently the power will go out at the house and I'll have water for quite a while until all the pressure is relieved. Same principal.
If however you think you have evacuated the lines and you still get constant pressure, yeah, your pump is still on. I think you would hear that running though wouldn't you?
