I suspect this might be someone's legit cell phone number that has been spoofed, or otherwise compromised for illicit calling.  The (864) 238-xxxx numbers are a block of numbers issued by Verizon Wireless to cell phone customers in South Carolina.  I have recently been receiving a flood of 864 number calls each day, many of them from either the 238 or the 301 (Union County, SC) exchanges.  The one time I mistakenly answered, thinking it was the number of a friend in an emergency, I was pestered with a cruise sales pitch.  I've been studying the trend online, and all of them are hucksters illegally pitching something or other.