MMI - iPhone synch solved
 

Quick version of FIX - GET A NEW SIM card for your phone, un-pair (forget) the device and car), re-pair the device with your car and reset the MMI.

OK, my iPhone 5 was at one time working perfectly with my 2010 A6 MMI. I could make and receive calls, access my directory, see received and missed calls, etc. THEN, one day all that stopped and all I could do was make and receive calls. This may or may not have been around the time I upgraded the iOS on my phone which seems to happen every few months.

The Audi folks were not able to help pointing to Apple as the problem. The Apple people (of course) pointed to Audi.

Then, one day I took my car in for some radiotor mount recall and got a Q5 loaner. Strangely, my iPhone paired perfectly with that 2012 Q5 and all worked well. Also, the mechanic working on my car had an iPhone 5 (same iOS) and his phone paired perfectly with my car. So, it was neither MY car or MY phone.

Then, I involved AT&T. After unpairing my phone, unpairing my car, resetting the MMI a few times, checking setting on my phone and checking settings in the car, NOTHING changed.

Then I asked if I could get a new SIM card. The technician said that this has NOTHING to do with the problem and would be the equivalent of standing on one leg and wishing the thing to work. I persisted. He changed the SIM card. I unpaired the phone, reset the MMI and VOILA, everything works again. He sat in my car in complete amazement as did I. He has NO IDEA why it worked but it did.

Hope this helps others.

Same problem with iPhone 5S and Audi A6 '09
 

However, my phone is new and so is the SIM card.