I have been receiving calls from this number several times a day, off and on , for about a month.  They call, let it ring 5-6 times then hang up without leaving a voice-mail message. When I try to dial that number, it says that it is invalid.  There are actually 3 digits more that display on my call phone after the number above.  They are 942.  I got a call last night at 0415 am and, again, they hung up without leaving message.  Then several hours later, they called back and actually spoke.  He had a heavy accent and it was difficult to understand him.  He did say , I think, that his name was Michael and he was calling from Nigeria.  He asked my name and I said that I did not know the caller and would not give my name.  He kept trying to ask questions but I couldn't understand him.  I just hung up.