Mailing And Change Of Address

[drma 3]

Hi I recently got a receipt (I-797C) to my mailing address (different from my living address) for the I-821 application but oddly enough got the receipt for the I-765 to my living address. Does anyone have the same case? Also I put the a different mailing address than my living address in case I moved which I have since the time I submitted my applications. What I'm worried about is the the AR-11 form doesn't ask me for a receipt number for reference. Do they use the A number to identify the application? should I put the I-94 number as they suggested in the I-821 nothing asks for my mailing address. Is there a form to keep the future paper work to be sent to my mailing address? I called USCIS and they told me that to change address it can be done online and i found the form (AR-11) and they also told me to change the mailing address i could also find it online but i cant find a form.