Hi! Yes! It is definitely worth calling and asking them. You may need to make more than one call until you get a person who has the authority to make that change, but it can't hurt to call and ask. I'd do a bit of research first to see what the interest ranges are that the credit card company operates in so that you know where you might fall. You could also send an email or letter to ask.
You also might want to see if there is a format or form provided online by your credit card company to request a lowered interest rate – that site will provide specific information to help you succeed in your request.
I feel as if it never hurts to ask for discounts and good deals. Many of us shy about doing this - I often am - but if you can get your courage up and try, you may be successful. Good luck to you!