I was getting sms everyday from grameen phone for the offers I don’t remember using them. So I needed to stop it somehow. There might be more ways to that but probably the easiest and cost free is by chatting with them on their website https://www.grameenphone.com/
Simply click on the chat icon on the right bottom corner of the website and ask them to stop the all annoying promotional sms. They will do it for you instantly and activate DND (Do not Disturb). As simple as that!