I have, unfortunately, not been able to find any information on what insurance group the Audi belongs to. I can only check the ones that are being sold in the market, like this one: https://www.vertumotors.com/new-car-deals/audi/a3/sport/250219/audi-a3-30-tfsi-sport-5dr-s-tronic-petrol-hatchback/ which are labeled as 15E.
Motability aren’t known for their accuracy, especially at quarter change’s!
I suggest a call to DLM, to clarify the group the car is in and question, if you still believe it is wrong 🙂