Thieving M-Web

I signed up with M-Web. Cancelled after a week as I moved to a new residence where wi-fi was provided. I only received a SIM card and MAYBE used 500MB of data, MAYBE. The original product price was R300 p/m or so. I even paid them R500 to get them off my neck, after cancellation. Now they handed me over to e debt collection company!!! Do you think I can reach them by mail? Nope. Pathetic. Stay away!!!!!!