There are teachers on italki who specialize in conversation (including me, casual American English), so I suggest you look for a professional who can help you become more comfortable speaking. You have the skills. Here is a correction: Hi, I have a degree in Language and an English school called me for an interview, but I don't know if I'm ready to teach English. I don't know anyone with whom to practice conversation. (More casually we would say: I don't know anyone to practice conversation with.) I'm afraid to teach something wrong to my students. I started to learn English on my own when I was eleven years old, and then at college, where I could work on my grammar skills. I finished college but I am still learning! So, the question is: Am I ready to teach? Good luck. (And I hope we are all still learning!)

If a language school thinks you are ready, you are ready. Many people learn "on the job", in all kinds of worlds. You clearly know enough to help an absolute beginner make a start - and maybe more. You might be teaching mostly from prepared lesson plans. Why not try the interview and see how it goes.

you guys are savage, agreed though.