What Are the Steps to Transitioning to a New School's Work Permit in Thailand?

I'm confused. Getting different info from my new school, someone at immigration and something I remember reading here.

I'm on an extension of stay from my current school. My new school is saying have my current school cancel my WP and EOS and that I have until July 31st and then I'll need to leave the country (with the other new teachers that are here on visa exempt stamps to get a new non B. (someone at immigration said similar)

Initially they said I could get my visa done (amended, transferred?) here in country like I vaguely remember reading something about here.

What's the real story?

Have things changed due to Covid19 or am I breathing too many motorbike exhaust fumes?

Thanks.