Fnb will not stop sending SMS

I have spoken to your complaints department about 10 times, requesting you to stop sending me SMS. I receive 3 to 5 sms per day, some come through in the early hours of the morning thus waking me up. Pls advise what I must do to stop receiving these sms. I have tried everything to get you to stop sending this, pls advise. I cannot block the sms because you keep sending with different number. I am desperate pls advise