Is the accumulated amount of administrative fees on an unclosed bank account considered a debt that must be paid before God?

As long as you did not close the account, and consequently incurred fees according to the contract you made with the bank when opening the account, and this was confirmed by informing you of these expenses and fees, then you are obliged to pay them. They are considered a debt upon you, due to the Almighty's saying: "O you who have believed, fulfill [all] contracts," and due to the Prophet's (peace be upon him) saying: "Muslims are bound by their stipulations."