I always say to people that I am happy to answer any specific questions that they want to message me. However, because I am an English teacher for my job, I cannot afford to spend hours talking online (conversation practice) for no pay. I take lessons seriously and will have to have prepared some materials for us to use. To me this site is supposed to supplement my income, as well as being a site for friendship and discussions. I also use the site to learn portuguese (which I pay for or exchange English for). If someone requests a session, I may change the time but I will accept it if I think that I can help you. If you just send me your Msn address though - you are unlikely to receive an answer.
I suggest telling the teacher what you really want. If you are here for language exchange but cannot offer the teacher a language that they are learning and do not want to pay for a session...you may not receive a reply!
Maybe a little harsh - but honest!