Most parents are aware that children need to have multisensory instruction at school in order to learn things like math, english, science, or history. But, many of us have not really thought about the need for the same strategies when teaching children how to answer the phone or how to behave when there are guests in the house.
Most people do not learn well when parents or teachers just tell them how to do something (or how not to do something). So when Samantha answers "Hello, who is this?" or "Hey!" when answering the phone, just telling her this is not appropriate may not be enough to help her learn the proper way to answer the phone. Listening is a single sensory input which does not work well for most people.
Instead of explaining that asking "who is this" might be considered rude, it is better to model alternative things to say. Then have the child pretend to answer the phone so she can practice the appropriate way. This is true for anything you want your child to learn. Modeling the skill for them and then having them practice works much better than simply telling them what to do.
I wrote a related post called Study Strategies that Match Your Child’s Learning Style. You might be interested in reading it too!