Telkom Unable to cancel their own landline!

I have been trying to cancel my Telkom landline for 2 months, but they state they are unable to do so as they do not have ownership of the line when we have not ported it or have another service provider for the landline. We have moved to fibre and no longer need ADSL or a landline, but still, they have not cancelled my line and still they are sending me accounts that they expect me to pay.