Well...the fact that you failed at ONE company (even if you failed twice) hardly means you can't be a pilot. Not in and of itself anyway, it's just their (that ONE company's) opinion. I will tell you this, though: not too many things are as important at an interview as good communication skills, so if even you yourself recognize that your English is perhaps not where it should be, maybe you should work more on that rather than on mock interviews. What you say is nowhere near as important as how good you sound saying it.