1. Restart your iPhone 7
2. Re-pair Bluetooth devices with iPhone
* Open Settings app and tap Bluetooth
* Tap i icon with the devices connected and tap "Forget This Device" - and confirm OK
* Search for Bluetooth device again and re-pair it.
3. Reset iPhone's network settings (Note: This will erase the Wi-Fi passwords - so take jot down the password to re-enter again later)
* Open Settings and tap General
* Tap Reset --> Tap Reset Network Settings (Enter passcode and confirm to reset by confirming OK)