Predatory Lending Practice

I'm an ex-employee of Standard Bank who holds an RCP account in which I enjoyed special interest rate as an employee. When resigning from Standard Bank Group in March 2015 I personally went to Florida branch with a payslip from my new employer in order to update my profile and I was accordingly told that interest rate on my RCP might change since I was no longer with the Group. Since then there was no change in interest rate up until I approached my branch in February 2016 to increase my limit and they approved with without hesitation. To my surprise, I have just received a letter advising of the rate increase from 7.5% to 23%. This rate change is app**** after I have increased my RCP limit, which put into question the Standard Bank's compliance with TCF. I trust that someone will pick up this query and contact me to sort this out.