Still billing cancelled contract after 5 months

I bought a Vodacom internet bundle, but cancelled it according to Vodacom's T&C's. They collected the unopened box and logged it on their system as cancelled and returned, but they are still billing me. After 5 months, 15 calls and 5 emails of which only 1 was answered they are still taking my money. Every time I call they cannot find any such activity logged on the system and I am met with promises of returning my money to me. <br> <br> This is impossible, I cannot believe the poor service and outright lies from every single employee I have spoken to.