Worst Service Ever - Just Cancel the service!!!!Stop Debiting My Account

I am disgusted with MTN service. I cancelled my LTE subscription end of July and handed the router. I was billed for August aswell as September. How am I being billed for a service that I cancelled 2 months ago and handed all the equipment. I even received an sms threatening to suspend my service. What service????******* please rectify this ASAP