Every time Terri uses Bluetooth with her iPhone in the car to make a phone call, the other side gets an echo. Leo says that it's possible that the phone is using its microphone, and the car is using Bluetooth. That can cause an echo. There could be a setting in iOS to use the car microphone when using Bluetooth. Leo also suggests un-pairing the phone, and then re-pairing it. That almost always fixes problems like this.