Well I have heard so many bad comments about studying English on the phone so i had half a mind to try it.
But while surfing on the internet, i found this website offers a trial class for free and

it really made me think trying wouldnt do any harm.
It was only 10 minute i talked with Alise so i dont think its enough to know how well she teaches.
But there is one clear thing i felt during the class. 
It is that she is good at helping  student keep speaking. She didnt try to cut off my slow words even with the time limited  by 10 minute, and, of course, she didnt forget to give me instant corrections.
Although there was slight noise at first, Im satisfied with the class and now i think i should have found this site earlier.