XM Radio Lifetime Membership Not Allowed to Transfer, Internet

I bought my lifetime membership to XM over the phone and was told by the agent that the membership was transferrable, I gave approx. $500 for the service. About 5 days ago I bought a new Chevrolet Silverado, after transfering my OnStar account I asked to transfer my XM account and they transferred my call to a XM agent. I was told my lifetime membership was non-transferable, I asked to speak with a manager and was told by her that lifetime memberships were never transferrable at all. I would have never paid $500 for one vehicle, I knew when I bought my membership to XM that I would be trading trucks soon. I always enjoyed my XM radio and I miss having it but I feel I have been ripped off.