fix a crack inside of freezer panels (plastic)?

Can someone please HELP! I have a AMANA REFRIGERATOR-FREEZER CAP. 24.8 CUBIC FEET SIDE BY SIDE, MODEL #WSSD25NBL.
Discovered a long crack inside of freezer approx. 20" long in length, need to know if anyone out their knows what kind of product works great to seal this crack. My concern is that my freezer is probably not keeping steady temperature because its escaping threw the cracks of freezer meaning my electrical bill is more expensive due to this problem.
PLEASE GET BACK IF YOU CAN HELP!
GREATLY APPRECIATED VERY MUCH.