They called and asked how I was doing. I said "I'm okay but I'm at work and you're probably calling to sell me something I don't want, right?" Silence. I then said "I thought so" and hung up. Also, when I called from a modem phone I got the same "we don't recognize your number, good bye" message. I'm just glad that T-Mobile has an "Add to clock list" option.
I receive calls from this number around the same time everyday. They don't leave a message and I haven't called back. Based on the other comments I will block this number.