Loud squeal when using LG HBS750 w iPhone 6+, how to stop it?

I am frequently using my iPhone 6+ and my LG HBS 750 Bluetooth headset on work calls over the past 2 weeks since I purchased both together. Since day 1 there has been random loud squeals/ screeches. Sometimes the customer hears it and I do not. Other times I hear it and they do not. Occasionally we both hear it. Most ti has happened was 3 times on a 1 hour conference call.

I am talking VERY loud, like the Bluetooth speakers shouldn't even put out out a pitch like that. I almost crashed my car once when it happened.

The phone is never more than 15 inches from the headset. Usually I am not touching the phone at all.

I am on Verizon and can see the 4G tower from my office window. I am planning to use cellular as my primary/only phone for work.

Questions

Is it the Headset or my phone?

Any way to resolve it?

Thanks!