I need to cancel my contract

<p>I am getting annoying emails daily from MTN regarding out of contract tariffs applying to my number, I called last month to cancel my contract and was told I have to phone in after the 06/10/2016. My step father has been using that sim card and he has now lost his phone this morning, I need to block that sim card and also want to cancel the contract but your call centre waiting time is ridiculous and the signal wasn't even that great which was hurting my ears of 5 minutes of broken music.</p>