Should I close my Secured credit card since I maxed it and I am paying every month for transactions?

Ok. I have a secured credit card with which I deposited $1000 and I maxed the credit card out which is secured with my initial deposit. For the last 3 months I have been paying basically about $100 towards the balance which the minimum payment is $20. Question i was trying to rebuild my credit but the bank has my money I realized that since they have money why am i paying interest on the transactions I did when I can close the account and save my money (interest is 18%). Will affect my credit since regardless the bank has my deposit. Your inputs greatly appreciated. Trying to save money here. Thanks