Terrible service

I left MTN 5years ago and today I'm reminded why. I got approved for a data only sim on 25July, courier was supposed to deliver on 28July but they sent me from pillar to post calling me every day to confirm my identity but never showing up or having HHT problems, only delivered on 3August. Sim has never worked since then, dialed *136# as instructed by the welcome message but nothing. Nobody is taking my calls, can anyone help me cancel this nonsense?