However, if someone keeps calling me for very unimportant issues, then I would ignore their calls, and check voice-mail later to confirm if it was important.
I expect to get down-voted for this as it is a bit unfortunate, but if people think they can have my time whenever they want for whatever they want, then I'm not going to have any time left for myself. Plus, if an important call does come through and I'm stuck talking to someone about something unimportant, then it's the important call that is going to be stuck in voice mail.