One should manage their expectations when reading comments or chats on French-speaking social networks: they are often written in relaxed French where spelling, grammar and punctuation rules are seen as unimportant, and are often meant to transpose how the writer would spontaneously speak in colloquial French.
In this case, my take is that the writer wanted to say:
[C'est une chanson dont je suis] toujours à l'écoute, ça !
The confusion in spelling of ça/sa is a typical grammar mistake among young French native speakers when they learn to write (from my own school memories, native speakers typically learn in grammar lessons about that around the age of 8/9). It is yet quite common among "uneducated" (no prejudice intended, I cannot find a better word...) native speakers, and is even frequent in "short messaging" language, because it is faster to type than ça or even ca on a French phone keyboard (you can find other instances such as eg. "ses" used for "c'est").