gas not pumping at the station...

[Benz300]

00 E430 4matic.

I simply can't seem to put gas in the car without the gas pump shutting off every 5 seconds. I do hear something weird as if there's a pump operating while I'm trying to fill up the gas. The sounds seems to be coming from where the charcoal canister is located. more over after every time the gas is filled a little bit and I take the gas pump nozzle out, fuel literally splashes back as if there was some vacuum build up inside...

I do have rough idle, and the low fuel light blinks along with the check engine light that came on.
I've already replaced the gas cap seal. that didn't solve it.

thanks in advance.