Bayport not reliable for full payment

Good day I took a loan with Bayport in 2017. Without fail I've been paying R757. I recently contacted them to ask how much i still owe and for a settlement letter as I would like to pay the balance upfront and full . They sent me the details and I paid on the 11th of March 2019. Now what bothers me is that an amount was paid up full but now no one from Bayport or debt collectors have received the payment yet .. debit order of R757 has been going off my account without fail and now they having issues with the full amount that was paid but apparently has not reflected on their side. Now how can a debit order be reflecting since 2017 and the full payment has not reflected ????

I am annoyed as they keep asking for I.D number. How many times must I give this information ??? I paid it I want my closure letter or be sure I take this further because no way in hell that my debit orders have been reflecting but this amount has not !!