Stop harassing me

I missed a debit order for this company. I gave them an alternative date and made an arrangement. They have been calling me non-stop despite having made the arrangement. What's the point in making an arrangement if I am called non-stop? When I ask Ayanda why he is still calling me after making a payment arrangement he tells me it's because I missed a debit order. I am shopping for another tracking company, don't bother calling me again.