I can't think of any way that pressure can be decreased due to added pressure.
Be that as it may, and it certainly still is ...
No matter what you do to the pressure or the temperature of the gas in that tank, the volume doesn't change. Any sample of gas always expands to fill the container in which it's confined. Its volume doesn't change until you either transfer it to another container with different volume, or else change the volume of the container it's in.