Overflow pipe question.

I am putting in a new bathtub. I need to raise my overflow pipe two inches. It is PVC pipe. I tried to loosen it last night but the thing would not budge. I have no idea what the prvious owners could have glued it up with. Just need to fix this one hurdle and I be able to have a new bathtub. Any advice. Thank you to all who respond.

cut it off and splice in a new piece at the desired length.

pipe

It may be PVC, but how is it connected?