This may be a CarPlay issue. I have the problem as well and it's outright dangerous. I was totally startled when driving back one evening on the highway with music at med low as I was having a conversation. I've contacted my local dealership and they'll look into it. I've seen similar issues with other vehicles using CarPlay.
Has nothing to do with CarPlay and ALL Levante's have CarPlay.
When I deliver a vehicle, I make sure to pair phone then call client. Once I call client, make sure to adjust volume with rotary knob while speaking with client. Even though you're using the same knob for music to adjust volume, you still have to adjust same volume knob for phone. Also to note, if you're volume on your phone is low, you'll have problems hearing. Make sure it's all the way up or to at least where you can hear though bluetooth.