they charge you a more expensive activation fee if you activate on the phone, so do www.xmradio.com
all you need is your radio ID, which you can get by tuning your Radio to channel 1. It might be 0 but I can't remember right now, I have no XM in my office :frowning:
If it doesn't work online (or you don't want to do it online) you can call and tell them it failed online. They'll do it over the phone for the same price as online.