Interest Rate change on Bond

Received a message last week that my interest rate on my bond has changed. Prime + 4.10%. This is an increase of almost R3000 on my bond. Tried to get hold of the pricing department for someone to explain this ridiculous rate but to no avail. There supposed 48 hour turnaround time is a false too as I sent this on Monday to them. A bonds interest rate is based on their credit profile, which mine has no issues with. They clearly are a bank that has grown too big to the detriment of their customer service. I have quite a bit of products with this bank and now after been a loyal customer for 14 years with no defaults on any of my bond payments, looking at leaving to a much more appreciative bank who will treat me fairly. Expecting an urgent response on this.