Migrate to Prepaid MTN

Submitted a cancellation of contract to MTN for 2 numbers. Received a confirmation email that the contract will be migrated to prepaid on the 13 December 2019. As at the 17 December 2019, the numbers were not migrated to prepaid. Called the retention department on the 17th Dec and was told to wait for an SMS and 24 hours later the numbers will be migrated. This has not happen, please advise why have the numbers not been migrated to prepaid? *** / ***