Spam SMS after porting out

I have ported to Vodacom, I still receive these spam messages: Yello, talk more for less on MoMo R10 = 100min MTN-to-MTN or R12 = 60min to ALL networks (1-day deals). Dial *120*151# or tap MoMo App - https://bit.ly/MTNMoMoDownload - Queries? 083 135 OptOut *135# Auth JR of FSP 46094 T&Cs How do I opt out without phoning 083 135?