Hey Adersh, it is often rather difficult to negotiate APR when it comes to paying off your credit card. If you currently have an outstanding debt, banks wouldn’t be able to offer a lower interest rate unless they closed your account. However, closing the account is awful for your credit score.
You could always try negotiating better rates for your future purchases with a bank. I suggest shopping around at: https://yallacompare.com/en/credit-cards/ – where you can find yourself the best deals in once place. Once finding the card you like, be persistent with negotiations whilst also being polite. You have to prove your loyalty for a bank to trust you – which in turn will lead to them being more likely to give you lower interest rates.
Also do you have the intentions of spending a large amount of money, in a small time period? If this is the case, you could contact the retention department at your bank. They often alter peoples interest rates for small amounts of time, as a promotion. This could be a solution if you’re only looking for a temporary change to your interest rates.