Complain - Unhappy with Telkom service

I took a Telkom contract via Mobi talk towards the end of March 2019. I specifically asked if the router does not work will I be able to return it and the consultant advised that yes they will collect it anytime. The reason I needed clarification is because I saw a lot of complains regarding Telkom network. She checked my area and confirmed that where I stay there router will work. I believed her as I've been using Telkom prepaid for quite sometime. Unfortunately with the router it wasn't the case. When I connected the router it did not work, no network coverage. Telkom consultants tried assisting with no luck. On the 8th of April I cancelled the contract and advised Mobi talk to collect the router and sim cards. Indeed they collected everything on the 14th of May 2019. Up to date Telkom has not cancelled the contract and I've been following up every-time I receive an invoice and I'm assured it will be cancelled in 24 hours. 3 days ago I received a call from their lawyers advising that I need to make payment. I do not have any Telkom equipment with me. I need Telkom to cancel this contract within 24 hours as they have been promising. I cannot pay for something that I don't have and they collected. I've given Telkom consultants all the reference numbers and collection slip and they confirmed they can see they have all the information on their system.