My student plan got more expensive after the first year.

So just to be clear: nobody is stealing anything. The conditions of the student plan are that you receive a super reduced price the first year and a reduced price for the following years. This is what you expressively accepted when you took the subscription.

You write that you called Adobe and your school. And that none has picked-up? Well, either you have taken a subscription via your school, and then you need to cancel via your school, or you have taken the subscription on the Adobe website (what I suspect) and then your school is not involved.

To cancel, go to https://account.adobe.com/plans, click manage plan and then click cancel. The early cancellation fee is half of the remaining due and that also is clearly noted in the terms, that you agreed upon and that you confirmed to have read.

Cancelling without a fee is possible each year in the last month of your subscription.

If now, you want to try to contact Adobe customer care to negotiate a cheaper exit, you can do so by connecting via chat. Adobe customer care can be contacted by beginning a secure chat session at https://helpx.adobe.com/contact.html?rghtup=autoOpen. Pop-up blockers need to be disabled! If the chat window fails to open, or is non-responsive, use a different device to start the interaction.
Support phone numbers may be found here: https://helpx.adobe.com/contact/phone.html. Kindly note that phone charges may apply.

(see also here: https://community.adobe.com/t5/creative-cloud-services/how-to-contact-adobe-support/td-p/11875703 or here
https://community.adobe.com/t5/account-payment-plan/how-to-contact-adobe-support/td-p/11843852)

I suggest that you stay friendly, it helps to get what you need. I doubt, however, that you get a refund for the last 6 month.