You can change your username in the Android or iOS app once every six months by going to the Settings menu. On Android you can find the Settings menu by opening the navigation menu on the left side and tapping Settings. On iOS, you can find the Settings by opening your Profile and tapping on the Settings icon on the top. From Settings, select the Account option and tap on your Username to enter a new one.
Alternatively, contact Customer Service at firstname.lastname@example.org providing your current Peeks Social username and the username it needs to be changed to.