@vic1212 I’ve never run into this myself, since I haven’t receive a call while backing up. That said, it would make sense for IntelliLink/MyLink/CUE to any and all features of the infotainment system while the vehicle is in reverse, so as to minimize distractions… but I’m not sure that this is, in fact, the case.
Perhaps Brand from @GM_Customer_Svc can help us out here 🙂
