OK, so heres the deal.

I have quit an EF school due to a number of reasons. EF is crap school as we all know.... but they did get me a visa. I got 7 months left on it and yesterday was my last day, so if I want to get a job somewhere else and get another work visa I would need the letter of release from EF right?

After the letter of release is written will my work visa be cancelled by the school or by the govt bureau in charge of visa issuance in my city? So, obviously I dont want this visa to cancel quite yet as I dont want to have to buy another, and I likely will freelance for the time being until im able to stomach having Chinese FT colleagues again.

So since I dont plan on working FT anytime soon should I even bother asking for the letter of release？ Once my visa expires in march if I apply for another FT job will they be able to get me a work visa if I didnt have the EF letter of release? And what steps should I take so I can keep on using this visa and not have them cancel it for whatever reason?