I'm also on a temporary work visa, and switched to a different company last year. I can share some info with you based on my own experience. I would add to other's comments that it is wise to have another job lined up, if you decide to quit, because of the regulations of your work visa. You are allowed to change jobs and move to a different company with a temporary work visa. However, you cannot have missed one day of work. That is, you will need a Constancia de Baja from your former employer; let's say that your last day of work was, for example, Friday July 4th. The contract for your new job would have to start immediately the following Monday, July 7th, with a Constancia de Alta to the new company. This is what my immigration lawyer told me, and naturally other paperwork from your new employer is required to renew your work visa. Of course, specific information on changing employers for a work visa is not available on the Migraciones website, so in situations like these, it is better to talk to a legal expert on the subject.
If you quit, the legal way to do it is to send them written notification. You would go to the Correo Argentino to send an official notice, indicating your last day of work. They would then be legally required to provide you with the necessary paperwork (including your last pay stubs, etc), so that you can present this paperwork to Migraciones when you renew your visa.
Best of luck, and I hope that things get better for you soon.