I think it is about a boy who has loved a girl for a very long time. Maybe they grew up together, but now they live far away from each other and talk to each other about their new lives. It's "so much sweeter on the other end of that receiver" because it seems like the girl has moved on, but the boy still misses her. In the second voice he tells her that she should have her fun where she is, because no matter what he will always love her. This is why he repeats "I'm already yours".
I think the third verse is about letting go of an old love. The boy knows that no matter what, a little part of the girl will always love him, but it is better for both of them the let it go. He has been there for her for too long without anything happening between them, and finally realizes that he was never hers to begin with, thus "I was never yours."
I can relate this song to my personal experience.
I think it is about a boy who has loved a girl for a very long time. Maybe they grew up together, but now they live far away from each other and talk to each other about their new lives. It's "so much sweeter on the other end of that receiver" because it seems like the girl has moved on, but the boy still misses her. In the second voice he tells her that she should have her fun where she is, because no matter what he will always love her. This is why he repeats "I'm already yours".
I think the third verse is about letting go of an old love. The boy knows that no matter what, a little part of the girl will always love him, but it is better for both of them the let it go. He has been there for her for too long without anything happening between them, and finally realizes that he was never hers to begin with, thus "I was never yours."
This is how I see it anyways.