Money requested for account paid up with Autopage and device fee which was never made known to me.

In Feb 2017 I received a call from Nimble Group informing me about monies owed to Autopage.I advised the agent (Mercia V) that I had paid up this account in full when handed over to Vodacom.I then provided proof of payment and received no further response.I then get a call today asking for payment again , again I advise this is paid up and I feel this is now harrasment.I email everyone I can regarding the payment made only to get a response from Colin informing me its for a device fee.Worse I get a copy and paste "statement" and not an actual physical document showing this.According to Colin I still had 5 months left to pay for my device.I paid this account in 2016 and closed it off why was I not alerted to this so called device fee.Also I do not recall been told that I would have to pay a device fee I want proof of this.Everything was handed over to Vodacom why then is Autopage asking for money for a device surely when I paid Vodacom my subscription fees the device was included in this amount my contract stated R249 a month which I duly paid to vodacom until the end.I have had contracts before and I have never been requested to pay for the device fee separately after the contract is finished.This make no sense.