The speaker is talking to someone who feels shut out and can't see why. The answer comes back again and again in the refrain: why trust a person who never listens and only kept them around for attention? Each time the chorus returns, it sounds firmer and more tired, as if the speaker has explained this many times and still hasn't been understood.
The verses fill in the story. The speaker hid their real feelings behind convincing smiles and laughter, and the other person was fooled. When the speaker did start to open up, the timing was off, and the other person pushed them away, then tried to restart things too late. The "wall" becomes the central image: it grows higher and stronger, and the speaker even thanks the other person for that. The mood is guarded, bitter and a little sad. There's hurt underneath the defiance, and a sense that the speaker lost something too by staying closed.