Upgrade/Billing issues

So after 6 years of using the same cellphone my phone got damaged irreparably on the weekend. I still have an existing contract for data and minutes so I think great I can just upgrade so that I can get a new device. How wrong was I? According to your upgrades department there is an outstanding amount on my account yet when I phone your billing department and check on the whatsapp portal there is an amount of R374 outstanding for this current months bill which is not overdue?!! Who or what do I need to do to get this sorted? The phone that I am using is barely usable. Should I cancel my contract and move to a different network? Your billing department and your upgrade department don't seem able to work together... FRUSTRATED