Non-stop spam, totally unbearable & unacceptable

For the past couple of weeks, I have been receiving non-stop spam SMS's on my Cell C mobile number - day and night, waking me up at at all hours of the night and interrupting me all day long (loan offers, phishing SMS's in the name of Omo, Toyota, RICA & god knows what all else). Since other customers have made the same complaint, I can only assume that Cell C is in the business of selling our numbers. I don't know how to make this stop, but if Cell C doesn't do something about it, IMMEDIATELY, then I am going to switch providers. This is totally unacceptable.