Whenever I fill my car with gas, when I start my car the rpms start jumping and the car sometimes stalls. It's not from over filling because it happens even after adding only a few gallons.
If anybody has done work with the evaporative emissions system or fuel tank, they could have swapped some hoses by mistake. Most likely though, just going off this one symptom and little else info, it sounds like a leaking purge valve (on the intake). If you can find it - it's typically a black plastic cone with a rubber house on each end, one vacuum to the intake itself and another back under the car towards the fuel tank, plus one connector, it would be simple to check. Once removed, it should hold vacuum (on there intake side) up to about 15 in mg. Also, you could pinch off the house with some clamps right before fill up and see if the problem is gone.