Interest rates now higher for no reason

As a standard bank customer for over 15 years I have never seen the interest rate on my vehicle go up with each car I buy. The rate I got on my last car was prime less 0.3. Now I was initially quoted prime plus 2.75!! After arguing with your JHB call center, the best they could come up with was prime plus 1.10. The past 2 cars i bought was below prime. Do you know who your customers are? or just take chances? This is unacceptable. Please explain why I am being charged are high rate! I rather move to another bank that appreciates my business. I my credit score is above 970 so dont give me that nonsense that it depends on my credit ratings.