Being wrongfully accused of non payment

I am being harassed by this company sending me messages reminding me to pay my capitec account. Because i do not have a loan account with capitec I called them to inform them that I am the wrong person and was promised that they will take my cell number off the system. I subsequently called them 9, times to request that they fix the problem but even over this past weekend they sent two messages. I believe that they prefer to ignore my request and when I wanted to speak with the supervisor I get told " not available" please advise! Kind regards