This seems like the same issue I had with my 12 Cruze. It was an LTZ but BT was phone only. I added a dongle to the car that worked fine for music but was horrible for calls. And using the built in BT for calls and dongle for music was a mess. I don’t get that many call so I ended up unpairing the car and just using the dongle. If I got the odd phone call I just had to scream to the mic.