called left a message,they were talking to someone with them, saying no they can't if they have a spouse

i am called from this number, no body talked to me from th,is number also. Iam in ıstanbul now. why this number comes to our phone.

call my mobile number

Called and asked for a friend of mine by name, and wouldn't leave a message, said they didn't have a direct number to call them back and then hung up on me.

Called after hours but did not leave a message.

They call with a heavy Indian accent by the name either Francis Wright or Keith McNulty harassing me at my job or personal phone over 50 times a day have my supervisor and myself has asked them to stop.

They've called me far too many times in this past week and they won't stop calling...how do I make them stop? I've reported them on the Nat'l do not call registry but they're not doing anything to stop this.

I receive calls from this number 5 - 10 times a week for the last several months. No message is left if I do not answer, there is no response if I try to answer. If this is some kind of billing scam, or trying to place a virus on my phone, I need help blocking the call. AT&T offers a blocked number service, but I do not want to pay for an extra service just to stam nuisance calls from one number.