New round of harrassment despite opted out?

After months of complying with my “ opt out stayus” MRN has started the harrasment again. A MOMO promotion again! Y'ello LIZETTE! You have YelloBucks, SPEND them on MTN Mobile Money (MoMo)! Buy airtime, data, prepaid electricity, pay for DStv & more with YelloBucks on your MoMo wallet. SPEND your YelloBucks on MoMo via MoMo App>>https://bit.ly/MTNMoMoapp>> Queries? 083 135 Opt out *135# Auth FSP T&C's. REALLY? Do I have to start writing MTN again?