Woolworths is spamming me

All of a sudden, woolworths has started spamming me over the festive season. I do not mind an occasional sms, but they are harassing me with marketing smss almost by the hour! This is without my permission and very unwanted. What's more is that the smss do not give me an option to opt out. I did not expect this from Woolworths. It is making their brand look very bad.