I was stationary but my engine was on and I was using my mobile phone until I read about it I did not know that your engine had to be off, I was in a safe place no other cars were around, I then noticed a DVLA van can they report me to the police?
To be guilty you have to be driving your car at the time you are using the phone. The definition of driving includes both motion and control of the vehicle. If you were not in motion then you have a defence.
The court may take the view that you were only stopped temporarily, or the officer may suggest that you did move off/slow down whilst using the phone, but if you are sure you weren’t moving you should reject the ticket.
Bear in mind that if you reject the ticket you will be at risk of higher fines and court costs if you lose at court.