Billed for equipment I don't have

I canceled the service at the beginning of October and even got the sim disconnected on the 31 of October I paid the final installment on the 1st of Nov

Now the 2nd of Dec I am getting billed for a device I no longer have

When I call the support line they keep passing me on from consultant to consultant Their service is ridiculous let alone the support services

I demand rain management to call me as they have my details as they will see the support tickets I logged

This is absolutely pathetic on their side