Quoted:
Go to the website , they are easy to deal with. I think its www.siruisxm.com , or something like that.
I got the 4 year plan for $400. , commercial free , great classical music , Jazz and 80's.
You know that you can get the lifetime plan for $399? Of course that is the lifetime of the radio, not the owner, and so far their equipment hasn't impressed me that much.
OP, the previous owner may have purchased a lifetime, or other long term plan for the radio, and the subscription is tied to the hardware. If he had wanted to he could have transferred it to a different radio.
Myself I have several Sirius radios and an XM, only two of them are active now. They shitcanned a couple of my favorite channels, and replaced them with stuff that was redundant before they added extra redundancy. I only have two reasons for keeping the XM, I really like listening to baseball games, and the radio is in my work van and I work in the sticks and don't get much FM that isn't Country or hip-hop/R&B, I am not much of a fan of either.