Charges for no device

Good Day. My partner and I, took a device from you with the hope of getting value for money from your establishment. Upon arrival of the device we contacted them again to return the device and to cancel the contract as it was not what I was looking for or promised. Their courier service picked up the device within 24hours of our contract cancellation. We have since sent e-mails to you with the cancellation form but after a year and half without the said device, we are still being charged.