Music Interface cable not functioning.

I bought an Audi A5 in January 2016 from Audi Johannesburg. I was particularly impressed by the music interface. I bought the car with the music interface. I bought The cable to be able to use this interface. The cable does not work. Many cables have been tried and none of them work. I drive a car without the features I enjoyed on my A4. At least the A4 had an Aux option. I am so disappointed and feel I have been sold a dud. Angry.