The water shut off valve going to the toilet is stuck in the off position. I purchased a replacement valve but I'm having problems removing the broken one. PEX tubing is used and when I try to remove the broken one the tubing just twists. There is a decorative chrome piece covering the pex tubing making it very hard to get a hold of with channel lock. I have never done anything with PEX tubing before, it there a different way I should be going about removing it? Thanks,