How to take frozen dispenser water line apart looks like waterline is in the white tube at dispenser

You can’t replace it. it’s in the insulation. You have to use a blow dryer to melt the ice in the line but be very careful not to get the plastic pieces too hot or you can wreck the whole door. GE does make a heater kit. but only for Metal liners.
We have had some luck with telling the customer to leave the dispenser light on all night with the freezer set at a warmer temp. When the unit hasn’t been used a lot. Owners out of town a few weeks or whatever.
Our area has a lot of out of state owners, second homes. So we see this problem a good bit. Shoot some steam up in there from the front. Then steam at the inside panel of the door liner directly behind the chute. I have had customers here who solved the problem by sticking a 1/4″ section of hard foam insulation pad (Home Depot- $4.00) over the area. It kept the airflow from freezing the area permanently. Beats replacing the door and making a series of callbacks. I tried it, and had no further complaints. I wiped the area with an alcohol swab to clean the plastic, dried it with a paper towel, then used an aerosol adhesive spray which is available at any hardware or A/C supply to adhere the pad.
Repair videos link on water dispenser issues. https://www.appliancevideo.com/?cat=&find=frozen+water+dispenser&post_type%5B%5D=post&post_type%5B%5D=premiumvideos&post_type%5B%5D=fromthefield&post_type%5B%5D=embdvideo