Failed the wrong car

Hi guys I need a little help, I was having a few personal issues and wasn't on the ball... Basically I failed the wrong vehicle, I took the reg off the vehicle and and checked it against the jobcard (turns out the reg was wrong on the jobcard by one letter and was a similar vehicle) and I failed it on the front plate being deteriorated so didn't spot that it was the wrong car until retest.  What do I need to do next? ive called the help line but im not clear what to do or what key to press or what to do... panicing a little!!