This is a collection agency. They are aggressive, rude and they use dirty tricks, most of which are illegal. If you get a text from them, it's because they are trying to trick you into giving them your current address. Be careful, they will even use relatives names (spouses, mothers, sisters, brothers, uncles etc.) or names of people that you know in order to get personal information. Block the number and write as many posts as you can about the number on-line.