RFE amendment document submitted in premium but still status not changed

I have submitted RFE amendment document and its in premium but its almost 20 days still status is Request for Additional Evidence Was Mailed.

How would I know that USCIS received my document or not.My immigration team is saying they have submitted the document.I am confused.can anyone suggest me what to do and to whom should i contact.

If attorney has sent response through service that can be tracked, then they may be certain that USCIS has received it.

There were reports that USCIS is unable to honor 15 day PP window and is refunding the PP fees. However, they are still striving to process ASAP but not within 15 calendar day window. Ask attorney to follow-up w/ USCIS on this deadline. Maybe the fees would be refunded.