No service or assistance

I have a 3GB mobile data contract with Vodacom. I needed the service to stop on reaching a zero data balance but needed to be able to purchase data on my contract invoice/bill and Vodacom said no problem!!<br> With the upgrade Vodacom said I would receive a new modem and a 500GB external hard drive. I got the modem which has not worked since I got it and 4 months down the line am still waiting for the external hard drive