Device charge dispute on contract

Hi, to whom ever who can assist regarding my matter with MTN, I took a contract iPhone 11, my contract came to an end 31/11/2025 last payment was on 01/12/2025 also received SMS confirmation that my contract is up i will go on month to month paying for airtime… received an SMS 28/12/2025 sms telling me an amount of R573 will go off on my account on the 01/01/26 , for what because my 24 months is up, called in customer care they telling me it’s device charge from where no one ever told me of a device charge even when I called in to confirm last payment date… please sort this out I know nothing about a device charge and I won’t pay it 🤞