Contract ending

I have 36 months contract with mtn from 2023 September I’ve been a loyal customer from R439 till now I’m paying R616 . So as I know there must be a reminder when the contract it’s about to end well mine it suppose to end on the 16 th of September 2026 . I did remind them earlier on august they rep**** to me saying I must wait for 20-30 days which is today. Today I was told I’m late while I have the proof of that email apparently I was supposed to notify them earlier which I did so now they gonna charge me while it’s their fault. I’m so ****ed. I need answers I’ve been loyal to mtn this was supposed to be my last payment