Then I found an answer others may wish to use. Our phone handset can store some 20-plus numbers and a huge selection of ringtones.
Enter all the numbers of callers you wish to answer and give them a distinctive ringtone. Then select a completely different melody for all other incoming calls.
If an unknown caller rings: do not bother to answer. If they need to speak to you, they will leave a message.
Geoff Hobbs, Morbihan