Who called from 6782119999

Throughout June kept getting calls from 678 888 9888 - tried repeatedly to get them to put me on "Do not call list" but they just hang up.   Now same people calling from this number and same response.   Calls appear to originate from India and spiel starts "I'm calling from technical department of..."

Got a call around noon and after I said hello 4-5x I heard "goodbye" and they hung up.