Annoying Vodacom SMSs

I have a serious gripe with Vodacom at the moment. Its not with the core business of providing a cellular service but with the constant SMS adds I get. Numerous messages per day. None of them have an opt out and `I have tried the STOP ALL I heard about. It doesn't work. I do get a message saying that my request to unsubscribe has been received but I never get the promised confirmation and I still get more messages. I've tried it several time over the last 3 weeks. Grr!