To crumple up a paper

You CRUMPLE a piece of paper - creasing it is to prepare making a paper air plane or origami

However once you have crumpled the paper, it likely becomes creased by your action, but that is incidental.

Other expressions

Wad up a piece of paper

Ball up a piece of paper

The latter gave me this strange synonym on one dictionary:
Gunch - verb; to ball up a piece of paper; usually used in conjunction with crinkle
She gunched and crinckled the bills in total disgust.
but I would not use it since it also appears on Urban Dictionary as something horrible and on hackers dictionary both with no reference to paper

A crease is just a sharp fold. I'm not familiar with "crease up a paper" as you were using it. "Crumple a piece of paper" or "Crumple up a piece of paper" are much more common.

As has been said, crumple is better than crease in this case.

Other possible phrases are:

ball up

screw up (into a ball)

scrunch up

all of which I would happily use and have heard others use many times.

I would say screw up a piece of paper, but I can't find any source online that confirms this usage. Perhaps screw up is overworked anyway.