there could or of two issues in play" 1. the salesman isn't knowledgeable about product features or 2. he lied to make the sale with a dealer inventory swap.
I would prefer to believe the former than the latter but could believe the latter......
The XM is optional for the XLS and included with the Limited.....
Not to second guess you, but did you check to see if the dealership did/did not register the car's XM ID?
One way to understand for certain if the car was equipped with XM is the sticker..... if it is - it will list the 90-day free trial. The last resort is to confront the salesman in the presence of his sales manager and see what they will do to satisfy your parents.
Sateliter enabled and capable ARE two distinctly different functions. Enabled means it can receive XM transmissions...... caable means the receiver can be added ( for mucho $$$) at the very least they ought to add the receiver.......JMHO