Coffee club information misleading

When looking to buy some coffee at Pick n Pay, I saw that Jacobs decaf was on sale for "coffee club" members, with instructions on how to join (you send your smart shopper number via SMS). Immediately upon sending the SMS, I receive a reply saying welcome to coffee club etc. So I buy two bottles along with my other groceries. After paying, I check my slip and - lo and behold - no special price for the Jacobs. I went to customer service, who told me, no, it takes 3 days to become a member after signing up. So why the immediate SMS saying "welcome", with no mention of having to wait before trying to get special offers. The sign on the shelf also didn't mention anything about having to wait 3 days either. I returned the coffee.