How can I be in Arrears

You Vodacom won't upgrade a prepaid sim to contract because according to you my account was in arrears. This is the important part, I have never not had funds in my account and I have never stopped a debit order. I am no banker but I assume if I have funds in my account and have not put a stop on the debit order, the debit goes off when you process debit orders. With this in mind, who's fault can it be if I was in arrears?

I have seen an entire day calling and being pushed from department to department without success. Spoken to some very rude and some nice individuals, the rude ones just not interested in helping and the nice can't help.