FNB Revolving Loan

I recently had an approved Revolving Loan with FNB which I was using for a few weeks, I paid the 15% of the balance for me to access the loan, to my surprise the loan is still not accessible, when I phone the Customer Contact Centre they tell me I cannot access it because I had missed a payment which I never did since I use FNB Account all my debit orders are in order and never missed a payment, I am so disgusted with how they treat me as a customer as a result I am considering switching banks especially after seeing complaints on their revolving loan from other complainants herein, I am with FNB for over 15 years but I think it is time to move on to another bank with such treatment