"change form" is a correct and usable phrase in written English.
You can use it to indicate a transition from one form into another. For example: "The caterpillar changed form into a beautiful butterfly."
Coupons will always be here, but they'll change form.
"They're going to have to change form," he said.
Currently, Polybot can change form but not in response to changes in its environment.
Stories change form freely as they inhale the air of each new age.
The worgen are the new Alliance race and have the ability to change form between human and wolf.
To store data, the interference pattern is recorded within a disc containing chemicals that change form in response to light.
Miracles, like subatomic particles in Heisenberg's uncertainty principle, seem to change form in the very act of analysis.
If not, the frustrations of the affirmative-action era may not go away so much as change form.
American officials have openly acknowledged those problems for many months, especially the ease with which financial supporters change form as soon as they come under scrutiny.
Through a popular misconstrual of their parts, and by a process known as "folk etymology", words can change form without much change of meaning.
The name Tetanurae, or "stiff tails," refers to another unusual feature, a transition point in the tail sequence where the vertebrae change form in a distinctive way.
