Hi Keith_ma,
welcome to the Apple (user-to-user) Community.
Re: "I cannot hear a phone call on my hearing aids with my watch"
Am no expert in this area, yet your post surely deserves a response.
seems hearing aids can only be connected to one device at a time, yet can switch between devices..
In Apple's article: Use hearing devices with iPhone - Apple Support
you can scroll to: "Use your hearing devices with more than one device"
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For pairing hearing aids to watch, in order to receive phone calls etc, this discussion thread may be helpful:
How do I attach hearing aids to apple wat… - Apple Community
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Your hearing professional / hearing aid supplier / may have help with your particular Philips hearing aids version.
or
You may be able to receive support from the manufacturer of the hearing aids: eg: perhaps they have an iPhone app for using the hearing aids with Apple Watch ... or firmware updates may be available:
https://www.philips.com.au/c-e/hs/hearing-aids.html
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If needed:
Apple's Accessibility Support Website
(NB: You can "Get Support" from the link at the bottom of their website:)
Accessibility Support - Official Apple Support
All the best :-)