Is there a way to pay an amount of my bill from my credit card

I actually don’t think it’s possible. But is there a reason why would you want to do that? 

@Sophia is right, you can’t actually set how much the preauthorized takes out as it only takes out what is required for the bill. Alternatively instead of having preauthorized setup, you can send the payment through a bank transfer instead as that way you can actually send however much you want, there won’t be limitations like specific balance that are shown in self serve the only down side is remembering to pay the bill and it takes a couple of days to process the payment. However like what Sophia is getting at, there isn’t any benefit of being ahead with a credit. It doesn’t improve your credit score or your standing with the company so there isn’t really any reason to.