Brakes have a scraping noise on low speeds?

Hello,

I have a problem with my car, when I I drive slow with my driver side window down I can hear a cyclic metal scraping noise the faster I drive the noise get faster too but disappears on high speed and it cannot be heard once I've left an enclosed place like neighborhood or alleys, in open area the noise disappears.

I had the car serviced from the Dodge dealer and told them about the noise but since they were asking for a heavy inspection fee and fixing fee of around $4,700.00 so they can change the whole of front suspension arms and the front shocks and all the brake rotors plus the front and back brake pads which even they said was in new condition from the last service so it becomes clear to them the knocking from the back which now turned out to be from the car's rear seat. I didn't go ahead with it but when I got the car back from them the noise was gone back then, the noise used to be on the passenger side with the passenger window down. Part of the reason that I didn't get it fixed from the dealer was also that they said the brakes discs cannot be skimmed since there are heat spots so all 4 rotors have to be changed.

When I gave the car to a local mechanic he said the discs can be turned but he turned only the front discs because he said there was nothing was wrong with the rear brake disks and again the noise was gone but now after I've driven it a lot the past few days on long distances and the noise is back the scraping sound is more prominent with the driver window down this time but even having the passenger window down you can some what hear it.

I'm just worried that it doesn't turn out to be the wheel hub or bearing problem because the Dodge dealership will rip me off.

What if it wasn't related to the brakes at all that's what in worried about and also while braking the noise disappears and is only audible at low speed in enclosed places.

Please advice me, I'll really appreciate your help on this.

Thank you,
Omran