MTN doesn't want to cancel month-to-month contract

I took out a month-to-month LTE contract with MTN online. Since April 2024 I've been trying to cancel this contract.

When I cancelled they said I need to take the LTE device in to a MTN store, the store doesn't want to take the device back without it's original box. I unfortunately lost the box (think the office cleaner discarded it).

I've been to the store multiple tmes and called and emailed customer care multiple times, but they don't want to cancel the contract. The stores keeps saying I need to talk to customer care, customer care says telephonically they can't help I need to talk to the store. No one responds to mails.

I pulled the contract and confirmed, no where is it stated that I need the device box to cancel the contract, only that I need to give a calendar month notice and return the device.

It's pathetic, the device is in perfect condition.