Hi Summervilledeb65,
welcome to the Apple (user-to-user) Community.
Re: "Oticon hearing aids can't hear my text messages coming in to my iphone 8: can hear my iphone ring
and I can talk and hear the phone conversation, but I it will not alert me that I have a text!"
You may need to check the settings on your iPhone 8, to ensure the notification sound chosen can be heard ok.
We do not know which iOS version you are using on your iPhone: The below info. is for iOS 16.
(If needed: try changing the iOS version by clicking the links below, choosing your iOS version at the top and checking the more precise details in the article.)
Apple support's article: Change notification settings on iPhone - Apple Support
says:
Go to Settings > Notifications > Messages.
Choose options, including the following:
✽ Turn Allow Notifications and immediate delivery for Time Sensitive Notifications on or off.
✽ Set the position, locations, style, and sounds for alerts.
✽ Choose when message previews should appear on the Lock Screen, and how they should be grouped.
✽ Set how many times to repeat an alert (from Never to 10 Times) below Customize Notifications.
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In Settings you can also change the volume of sounds iPhone plays when you get a call, text, voicemail, email, reminder, or other type of notification.
From: Change iPhone sounds and vibrations - Apple Support
Go to Settings > Sounds & Haptics.
To set the volume for all sounds, drag the slider below Ringtone and Alert Volume.
"You can also change the sounds iPhone plays for certain people.
Go to Contacts , tap a person’s name, tap Edit, then choose a ringtone and text tone".
All the best :-)