Sonata Bluetooth Issues

I have been experiencing some significant issues with Bluetooth on my iPhone 6. The most significant of these is in my 2011 Hyundai Sonata with the Nav radio. My iPhone 4 and 5 have both been seamless with the Sonata, but the 6 not so much. Here are the issues:

• The phone does not always connect automatically when the car starts. With the iPhone 4 or 5, it was rare that it wouldn't connect. The iPhone 6 connects probably about 50% of the time.
• When the phone does connect, calls are frequently stuck in "Private Mode," thus defeating the purpose of the phone Bluetooth.
• When a call comes in, the phone number is displayed on the screen, broken strangely with a +1 in front of it. The phone's screen has the name of the caller as stored in my phone book. With the previous iPhones, the name of the caller would be displayed on the screen.

In general, the +1 thing on phone calls is different from previous iPhones, and kind of annoying. I fully admit that I am not the most technical of people, so there may be an easy setting fix for this. However, I haven't been able to find it.

Here's what I've tried to resolve the issue:

• Reset the phone
• Reset the car stereo
• Delete and re-pair the phone
• Reset all network settings
• Restore the iPhone

Anyone have similar issues, or have any suggestions for a resolution? Thanks in advance for any responses.