What will happen if i refuse to re pay my train fine?

2 years ago i got fined on a train for putting my feet up on the seat, i had payed it and went overseas for over a year, i have been back now for one year and they have sent me the infrindgement again saying i have an outstanding fine which i need to pay or il get a court order, i have spoken to them and they say have said to me to show them proof of receipt, now no one keeps receipts for that long and i have tryed to get my fines revoked and they have refused it and have ordered me to pay it again, I HAVE REFUSED TO PAY IT AND WILL NOT PAY IT UNDER ANY CIRCUMSTANCES. does anyone have any idea what will happen if i refuse to pay it or is there any other way i can get my fine revoked cos wen i ring them up theres no point, they keep sayign i have to pay, can anyone share a solution to my problem plzzz..im so stressed out..thanks and plz no rude answers :(