How to use the Apple® built-in hearing aid controls, for iPhone® and iPad® devices
All Oticon hearing aids with 2.4 GHz Bluetooth® technology (e.g., Opn, Siya, Xceed, Xceed Play, Opn S™, Ruby, etc.) can be used with Apple devices to make adjustments to hearing aids, including changes to volume, program changes and the ability to turn on Live Listen (turns the phone into a remote microphone).
To access these controls, you can select Setting > Accessibility > Hearing Devices and then select your hearing aids.
You can also access the controls by using the Accessibility Shortcut. To set up the Accessibility Shortcut go to Settings > Accessibility > Accessibility Shortcut and from the list of items select MFi Hearing Devices. Once setup you will be able to access the hearing aid controls by triple clicking on the side button for iPhone X or later. For older devices quickly click on the Home button three times.
Download instructions here