Transfer Credit Keeps Getting Removed

Has anyone had this issue before? We have one main parent account which includes 3 child accounts on it. The parent account is where all payments and charges occur. A year ago, Comcast applied a payment to one of the child accounts which now has a credit sitting on it. However, on the parent account side, they still say the amount is owed. I have called numerous times, almost once a month at this point, and explained that I need that credit transferred over to the parent. They authorize the transfer, but at the end of the month it seems the system automatically removes the credit from the parent and puts it back on the child account. This is very frustrating because it should be a simple fix but I am constantly on hold for hours to basically get nowhere. Has anyone had this issue before or have a solution?