How long did it take after completing your course to start receiving interview calls?

Actually, I already had an interview and was told I need to have a TESOL certificate in order to get a work visa.

I'm not getting any calls about interviews.

Let me tell you that I got my first interviews before I started working.
This was great. When I told them I will pass the Uni-prep Tesol exam as soon as possible, they just say : " Fine, we are waiting for you !".
So, I started working immediately.

Well, as for me, after getting TESOL I've started to look for job oppotunities by myself. It took me about 3-4 days to find several offerings and I just sent my CVs, in a 2 days after it I've recived invitation for an interview.

This course provides no assistance with job hunting and won't be providing your info to any schools seeking teachers, so you will not receive any calls just because you take the course. It's up to you to find jobs and apply to them.