Hi Barry, I have the 2016 A8L and I am fairly sure you don't need a specific vehicle SIM card. You should be able to use any SIM in the slot. I just bought a pay as you go data SIM card from 3 pre-loaded with 15GB of data or something and this works fine. I use that SIM only for Audi connect and then use my mobile in the phone box connected via Bluetooth for making voice calls. You can configure the in-car sim for voice as well - how have you set yours up? Have you tried something similar and just use the in car-card for data and your mobile for making calls?