I recently replaced an old StarPlus phone system with Asterisk and SPA504 phones. According to the spec sheet the 504 is hearing aid compatible but a user is having problems on the new phone. She is complaining of squealing and other hearing issues on the 504. She did not have any issues on the old StarPlus. We've tried adjusting the handset volume with no luck. Are there any other adjustments that can be made to the phone that might help with a hearing aid?
I've considered trying a headset to see if that would help or another type of phone. Any ideas?