H3's were built with any array of XM options. We built with out ONSTAR and XM, With ONSTAR only, with XM only, but the majority had XM and ONSTAR. I think they told you a lie when they said you had to get a Navagation to get XM as we had base H3's with ONSTAR and XM and single disk CD players. The antenna on top was for XM and or ONSTAR so it is hard to tell from the fin antenna if it has 1 or both.