Overcharging

I cancelled my contract on 30/6/2015. I was told the settlement costs for early cancellation was 3100 and another R430 for the last debit to go off. I paid this amount on 30/6. The debit order still went off on 5/7. So I double paid that amount. On my next bill, I got a R145 refund. They also still charged me R67 for my device, despite the contract bein paid up and cancelled. I spent 47 minutes on the phone with the call centre and no one was able to help me. The accounts person I eventually spoke to said ahe can see I was double billed and should get a larger refund. The refund that was sent was still only R147. You guys need to sort this out, cause I am fed up with your incompetence.