Daily spam, despite complains logged

Telkom sends me the same SMS almost daily, with the same offer. At first I didn't respond, because I simply did not want the service offered. So they kept on sending the same SMS over and over again. I phoned their call service and logged a complaint. Alas. Nothing changed. We already have three different accounts with Telkom, it appears that they still want more and don't accept NO for an answer.