When someone asks me to say hi to someone else for them over the phone, I never pass on the greeting but always tell them said person says hello back
That seems a little odd, why do you bother doing that?
It's just something I do. No real reason behind it.
It's not good to lie about something small like telling someone else they said hi. Just refuse to pass on the message if it's that big a deal to you.
You're probably right, I guess my behavior is pretty disagreeable.
It's good that you now realize that it is wrong to put word's into someone else's mouth. You'll grow as a person by being willing to change this quirk about yourself and that's great.