Resigning from a hakken kaisha

Hi! I would like to ask anyone here for advice,
I already have a job offer from another company starting November.

But my contracy here in client company is until end of November.
I told my hakken that i am resigning just this September, but they told me they want me to stay until end of November.
Can i push through my resignation? I mean it is written in my contract too that i can resign as long as 30days notice is given.
I don't know why they keep reiterating to me that my contract is until end of November. Am I being a bad employee here?
I don't know what to do.

by Awawawmeoww