LCD Pin Numbering vs I2C Controller Pin Numbering vs Sketch
Yes, the pins can be different depending on the LCD and the controller. My favorite solution to this is to run a simple "i2c guesser" sketch that can be downloaded from the following forum thread (download link is at the bottom of the first post):
http://forum.arduino.cc/index.php?topic=260510.0

With that sketch it usually only takes me a couple minutes to find the correct pin numbers.