Migration has turned to be a nightmare

i had a 24months contract with mtn and this year in February our contract came to an end , i have since decided not to upgrade due to financial constrains, on Monday i had a call from customer service from mtn telling me that i am eligible for upgrade and i told her that i have cancelled my contract with them and have since asked to me migrated to prepaid and she said on their system it does not show the cancellation, no i feel like mtn is forcing me to continue with the contract and i feel its unfair. i started calling mtn to cancel the contract in the beginning of February and i was told that i can only do so on the 25th of February of which i did and i was told that it has been cancelled, the following day when i called to confirm i was told that it does not show on their system that i called them the day before, i even received emails from MTN asking me to confirm my personal information of which i felt it was very unprofessional of them to ask me such question via e-mail. two weeks back i called again and i was told the contract has been cancelled and i have been migrated to prepaid now on Monday i am told that the migration has not taken place.