Been ****med by mtn

I canceled my contract I was even told I must pay penalties since my contract is still far from ending after paying I was told my contract is canceled I can now relax 2 years later I go to mtn to apply for cellphone contract to my supposed am told I owe MTN 2865 of a Dara simcard that I paid fully for n I was even charged penalties which I paid I never used the simcard and it shows on their system it last worked in 2022 when I closed the account