you can't change the text inside a symbol instance at the moment.
where did you get textVariables object? I don't think it's part of the Illustrator DOM.
...I meant, without breaking the link to its symbol.
I got textVariables somewhere on the internet. Just trying whatever to make it work.
I am used to working with Flash and movie clips so thats why I though I could change the text.
Is it possible to unlink the instance and change the text?
I am currently just putting new text on top.
yes!! use the "breakLink()" method...omg, I have not noticed we had it, it's been here since at least CS6. I used to break it old school, by deleting the parent Symbol.