I have severed doubts that, if you truly had gone back and paid within the 10 minute time scale, the petrol garage would have called the police
You gave your details knowing full well you couldn't pay/were not intending to pay.
To do so once could be seen as a mistake, but twice? You knew what you were doing. You knew you were stealing and you must know now you will face the consequences.
Stop dilly dallying with half truths and part stories. If you want those who can help to help, tell the whole story