Bad card service

I have had a credit card with standard bank for the past year, it was a gold credit card and I was doing good on my repayments, I was called by a standard agent to upgrade my card which comes with a lower interest rate, my card was upgraded however my interest rate remains the same, I have tried to get this fixed by making endless fruitless calls, being told that my call has been noted, it's been 3 months and everytime I call, they tell me they will call me back, it has been 3 months