-2,147,483,648 just happens to be the largest negative number that can be stored in a four-byte "long integer". The number can sometimes be seen in unexpected places, especially if there's a software glitch (see
http://thedailywtf.com/Articles/Please-Drive-Thru.aspx for an example). It's just coincidence that it's a 10-digit number starting with "214", the area code for Dallas, Texas. Most likely, if people start getting calls from this number, it's because someone with some computer programming experience is spoofing the number.