radio buttons have stopped working

The "auxilliary" button on my factory installed radio, where SiriusXM is attached, has stopped working altogether. I have a warranty and took it to the dealer for it to be repaired. They "reset" it and it worked, for a few hours. However, the next day, as I begin my commute to work, it again isnt working. I have already spent 4 hours at the dealership waiting for it to be repaired correctly, have taken the car home, and now have to return to the dealer a second time because once again, it isnt working. I am told that the dealership has to make 3 tries to fix the problem before they even take the malfunctioning area apart to see what the problem is, and that this is all on me. That they have no responsibility to make it right. That the warranty company calls the shots and I am not entitled to have it fixed right the first time. I know this is a small thing, but I commute a long way each day and having access to this part of my car is important to me. All I want is for them to find out what is wrong and fix it. Not really rocket science....but as a customer I expect not to be jerked around 3 or 4 times because no one wants to take responsibility for this warranteed part. Help.