Gold plus warranty on fuel pump and still have to sign for $125 diagnostic fee?

[Knockoutpie]

Hey guys I have a 2013 370z that has a gold plus extended warranty and service plan. Brought it into the dealership today to get my fuel pump replaced (as soon as I hit 160mile range on the tank it will drop down to a 24 mile reading in under 5 miles) I know this isn't fuel starve or anything because it didn't do this months ago. So I'm aware I have to pay a $100 deductible but they're making me sign a diagnostic fee for $125? Obviously I wasn't happy and threw a fuss.. I ended up saying that fine I'll sign the paper, but if you charge me $125 and not fix anything I'll just make a claim on it with my credit card company saying that you provided no service for what you charged.

Anyone else being forced to pay diagnostic fees with a warranty still on the car? I even showed them a video of what's going on and he tried to bull **** me saying "oh that's normal"

Sorry, it's not normal for fuel reading to drop from 160 miles to 25 miles and then back up to around 90 and drop way log again in under a 5 mile driving period keeping it under 2000rpm.