Bad Service

I took a contract with MTN so when i wanna activate the Router at the Galleria Mall they said i took it online so it got no coverage it wont work in my area and i should leave it in the shop they will book it to be collected and we cancelled the contract and i even got a IRMS Number for cancellation but i was shocked to get a statement that said i should pay R2794 and it in Arrears so how can i pay for something i ddnt use and i cancelled it in time of 30 days please sort it cause i cant pay something that i ddnt even open it please 🙏