I am going to suggest something: Get mad.
Part of the reason you are not being respected is because you are not
standing up for yourself and are instead playing this passive game of cat and
mouse. This just becomes an arms race that will go nowhere other than for it
to spread to other parts of your life. If you send the message that 1) you
didn't want the phone, 2)having it forced on you makes you mad, and 3) you
are willing to make interactions with family members who interject themselves
in your life acrimonious they will back off.
This is what you do:
1. Set up a phone number and voicemail using your preferred sip set-up
2. Move your cell number to it
3. Toss the phone in a drawer and forget about it
4. If someone makes a comment about using your cell phone simply say you
moved the number and don't use it anymore, but you will get the messages. If
they persist get mad and have a verbal fight with them, they don't have a leg
to stand on, and they can't make you carry it. If you start making it
socially costly for them to push you they will likely back off.
Sometimes you have to take respect instead of waiting for it to be given.
