One reason is that you are possibly being charged for spam text messages. In a letter from the customer service department, my provider tells me that in three weeks it has charged me a whopping Bt413 for such spam. The provider tells me it has 40 million customers. Do the maths on that.
My provider is probably not alone in this thievery. But there is a way around it. You can opt out of receiving spam. You can call customer service and have them cancel this “service” for you.
Of course, the ethical policy would be to not steal money from customers in the first place.
TJ Korst