Extra R100 charged

I opened a new contract with Vodacom on the 21st December 2015. I was told that a Once-Off fee of R163 will be debited from my account within 48 Hours. 2 days went passed and no money was deducted. They R163 was in my account for 2 weeks and still nothing was deducted. When I received my invoice for January 2016, I saw that I was being charged an extra R100 on my account. I went to the Vodcom shop in Kolonnade and the consultant told me it is because of a late debit order that wasn't paid. I was told to email my invoice to Vodacom so that they can look into the situation and everytime I call them they say it is pending and I haven't heard from them since.