They have no idea what's going on in their accounts

I've been a loyal Vodacom customer for many years, and I've never had issues with my account before. The past two months my bill has been very high, almost R1000 more than usual. I'm on a top up account so it's not supposed to fluctuate as much. I work in Namibia so I spend one week in SA and one week in Nam. I have a dual Sim phone with a Sim card for both countries, so when I go to Nam, I switch off the south African one and then put data on the Namibian card. I've been doing this for about 3 years, I never receive any calls or SMS messages on my SA number when on the other side. In December I had a crisis while cross border and I had to switch on my roaming because the networks were down that side. I was fully aware of the extra charges, so I switched it on, did what I had to do, and switched it off. In the following days I never received another call or SMS on my south African Sim, I got all the missed calls and delayed messages when I arrived on the South African border as per usual. I came back for a week and went back over the border a few days later. Again, I switched on my Nam card, put data on it, and got all my missed calls and SMS messages on my South African phone when I arrived on the border, as I always do. So after sending emails and receiving no feedback I went to a Vodacom store this morning, and was told that my roaming has been on for two months. This is inaccurate, and if it were the case, it means I am paying ridiculous roaming charges, and I still only receive all delayed communication when I'm back in the country a week later, so I've then been paying for a service that doesn't work in any case? And seeing that I spend half the month here and the other half in another country, how is it possible that I've been paying for roaming charges even while in South Africa? I am very, very unhappy. I have two contracts with Vodacom, of which one can be canceled in April. Given the service I've received, I am definitely ending it and then waiting for the other contract to end so I can move to another supplier. Neither the consultants in the shop, or customer service could assist or give me answers, they all said that they don't know how this happened, because if my roaming was on, shouldn't my messages and call come through in Namibia as well? The service has been utterly pathetic, and the lack of service is costing me a lot of money. I am not happy, can someone please look into this urgently?