2001 Vauxhall Vectra

Hi

We have a problem with our petrol flap on our Vectra. When the car alarm is on you are unable to open the flap, however today when I tried to fill up with petrol I was unable to open the petrol flap, even thought the alarm was not on. I have tried forcing it open, however this has not worked either. Can you help - with out being able to open it I cant get petrol in and I am stuck at home!

Thanks

Sheridan