boot area rattle

[JexL]

Ok so in my polo there is a bit of a rattle/ticking sound in the boot compartment like above the rear right wheel. Pretty sure it's within the body panel. So took to my dealer to get it checked out and they are trying to blame it on my rear sway bar. The thing is the noise is nowhere near the rear bar, only exists on the right side and came about well after I installed it.

Is it the dealers responsibility to prove that the bar is making the noise? Or can they refuse to fix my problem because they suspect it's from the rsb?

I know it isn't hard to remove the bar so I could always take it off myself in an hour but that takes effort and time. Or I could pay to get it removed but then if the noise still exists then I would of paid money for nothing due to them being lazy.

Going to call back the service department soon any advice?