So I am trying to replace an old soap dispenser and the nut underneath is completed rusted. Any tips on getting it off? Not a lot of room for a wrench. I have tried channel locks and a half a can of wd40. Any help would be appreciated.

Purchase or rent a basin wrench, (see image) and put a 10" pipe wrench for leverage. Could you get a hacksaw on the nut to cut it out? Good luck, Tom

Thanks Tom. No room for a hacksaw.

No room for a hacksaw. Simply take a hacksaw blade, Wrap a rag around it for a grip and saw away. Good luck, Tom

Multifunction tool at Harbor Freight $20. Forget Harbor Freight blades. Get Imperial brand blade.