Bad customer services

I entered into a top up cell phone contract with vodacom and come March 2019, two invoices were issued on my account. First invoice issued on the 1st of March 2029, which is a normal invoice that I get on month to month basis and come the third of March 2019, another invoice was issued again that made my total invoice amount to double. End of March 2019, Vodacom double invoice me and when I call their contact center, I was told that they cannot assist me because they are not working with invoices. I was later transfer to accounts section and I have been waiting for the last 2 hours without any help. Vodacom customer service is such mess