回复：请教NIW RFE补件材料可以自己提交吗？

yes, of course.

But you need to end your lawyer's service first via a written notice and tell USCIS to remove their contact information from your case. Otherwise you will probably get trouble if your lawyer wants to make trouble for you if they think you owe him/her money.

Make a clear end with your lawyer's service and keep all records properly in case you and your lawyer go into lawsuit process later on.

To avoid any potential traouble, pay what you are supposed to pay based on the signed contract and the service they have provided.