MTN is ****

Bad at service delivery. My mom has a contract with MTN and she happened to change banks so we've been paying manually and no debit orders since November 2019. Last month on 24 December 2019 I made an eft and sent them a proof of payment, MTN even sent my sister a message confirming that they recieved a payment but both their phones are blocked. They can't make any calls. I don't understand what must happen now because the money is paid. Why is MTN not unblocking the phones? Its 6 days today. Can't they see that the phones have been paid?