Pizza Del Forno Honeydew keep spamming my cell no

I have tried to opt out of SMS advertising by Pizza Del Forno Honeydew by replying STOP to their messages numberous times. I eventually got hold of them by phone and asked them to remove me from their database seen as I don't even live in Johannesburg! They promised to do so but they are still spamming my number! When is this going to stop?