Loan never ends

My last loan payment was suppose to be end February but they only debited half. I called and they advised the debit order already went through and I will have to wait for next month debit order. Come End March they debit the other half. Today I receive a sms that I still owe R35, why? and why not they deduct everything but instead split the last payment so that they can add more interest. On top of that each month when I get my credit report it shows a late payment however as soon as my salary comes in they deduct. So each month they just add more money that I owe and still give me a bad credit record.