Allocate payments as they wish

FNB has continued to mess with my credit score. Then they fix the problem and my credit score increases, then they mess me around and my credit score decreases. Whilst i acknowledge that my account is jn arrears, I have committed to an arrangement which i have stuck to. However, according to FNB, they can allocate payments as they wish due to my account being in arrears - emailed response to me. Therefore FNB, i have embarked on moving as many of your corporate clients away from you. Thus far, you have lost 2 corporate clients, who are my clients too. Lets dance FNB.