Won't stop promotional spam smses

Have requested to stop receiving MOMO promotional smses every single day for the fourth time. The *135# number you provide on the sms to unsubscribe does not give you an unsubscribe option!!!! So I have phoned twice, did what I was told, emailed twice and I still receive these smses to this day. My contract comes to an end in November, if this little issue is not resolved it is going to lead to me not renewing my contract.