Mailing address was changed but I did nothing.

[Abdul Shakoor]

My wife is US National. She submitted petition I-130 the case is going to process in NSC. On 17th July, The Alien Registration number was changed. Two weeks ago I checked the status on USCIS Website it shows "On July 17, 2014, your address was changed relating to the I130, IMMIGRANT PETITION FOR RELATIVE, FIANCE(E), OR ORPHAN that you filed."
I did nothing with my case. How the address changed??i got confused.
Please help.