Cancelled contract without a notice

Since 7 January 2022 I've been following up on my phone that was deactivated by mtn on the 28 of November 2021 and MTN cancelled my contract without a notice. I sent them receipts([Proof of payments for all the months)I'm still disputing that R16 974 because I never cancelled any contract I've been paying well its only one month where I made late payment. Its not Fair that they will charge me R16 974 for a contract that i never cancelled.