Loan Shark interest Rate Increase

I moved to FNB as they provided \personalised\" interest rates. I app**** for an overdraft on my account and received a high but acceptable interest rate of 13%, increased my overdraft to close other accounts with high interest rates and received an interest rate of 17%, which is crazy and queried, and was told interest rate will remain unchanged unless I provide surety. Now I receive an email with overdraft increase to 23.95%!! This is beyond ridiculous and bordering on loan shark. This is a \"personalised\" interest rate for someone who has never missed a payment and has a good credit rating!!"