Just try to imitate someone else way of speaking. I usually go for British accent , because I've watched enough British tv to effective imitate a few of the various accents from the UK .it's a trick I was taught by a speech therapist in middle school. its effective a good amount of the time, but I feel silly .also if im stuttering pretty badly ,the accent will slip out. which makes me a bit embarrassed ,and has led to a few co-workers ,and random acquaintances asking if im British .for me the trick is a crutch,and I try hard not to lean on it, but for over the phone ,one time calls it usually works .