Eflow make this mistake all the time, I used the M50 on Feb 19th, paid bill on 20th and got a fine in the post today, I phoned them and told them I have the time and date for the payment but seeing as they are so incompetent and have mislaid/lost/misfiled my payment that I was not giving them the time or date of payment - their problem - not mine.
I was on the phone for 15 minutes and told them that I am self employed and charge by the hour, I am sending them an invoice for my time in correcting their error, I charge €80.00 per hour and would charge them the minimum charge of €40.00. The invoice is going in by registered post today, I will go to the small claims court (€15.00 added on to my nivoice to them) to collect debt if they do not pay up, this should stir things up a bit.
If everybody that has proof of payment was willing to charge Eflow for the time spent correcting Eflows mistakes they would soon get their act together.