I was getting constant phone calls while I was traveling overseas especially in Africa. I know I was not the most civilized when I reacted at one point but I pretty much yelled at them stop calling me especially I requested not to call me several times. I didn't want AT&T graciously take my money away from unanswered calls from HVC. Since then, it worked. I vividly remember it was at the Ethiopian Lounge in Addis Ababa.