Depending on the level of the job you are applying for, you may wish to send correspondence by mail or make a phone call. In your reply, you should thank the interviewer for the opportunity to interview for the position and remind them of your interest in it. Advise them that they are welcome to call anytime and provide them with a reliable contact number. If others will be answering this call, let them know that you're expecting a call. Don't forget the proverbial saying, "The squeeky wheel gets the grease." Just don't become a pest!