Unfortunately, the calls will keep on coming. Terrible when self employed dependent on new clients not in your contact list and voicemail message is to leave message, text or email. When I am with a client, that is their time and rude to answer - wife knows not to call...but I can sneak a look at messages from her and others, and judge critical nature of issue for followup - immediate crisis (on way to ER) or general (loaf of bread on way home).
Overseas, international rates apply, paying for people wanting to buy my house or sell me a warranty on a car I traded in three years ago. Worse, checking voicemail is a phone call with international rates, so text/email only which is for me free, and if need to call, coordinate FaceTime/Skype connection.