Hollard insurance is a participating member of the National opt out database, but still sends unsolicited spam

My details are registered on the National opt out database (https://www.nationaloptout.co.za) On 6 May 2016, i received a spam SMS advertising Hollard insurance. Either Hollard should withdraw as a participating member, or they should stop sending spam. Furthermore, if a large company like Hollard can completely ignore the opt out database, what is the point of having an opt out database. For all I know, they got my contact details there. I have tried everything to stop spam SMS, but nothing seems to work. Very frustrating.