Bad service

I phoned Vodacom on Wednesday 22 August 2018 about an invoice that appears on my statement. It took a long time for the consultant I spoke to first, to find out what the additional amount on my statement is for. It is for the handsets I upgraded to in July. As with any upgrade the arrangement was that I pay a monthly installment for the handsets along with my monthly subscription. Suddenly I am invoiced for the handsets as well. I e-mailed all the relevant documents to a lady at Vodacom. She said she will immediately forward it to the correct person and cc me in the mail. So far nothing.