Is this a native I2C display or a standard HD44780 type with a backpack?
A link to a proper datasheet or a full part number would help. There are two common I2C expanders used with displays, the MCP23008 and the PCF8574 you would need to use a matching library.
When it comes to native I2C displays, things can get a bit trickier, there are several types out there, I have used a Raystar one which uses an RW1063 interface this appears to be roughly the same as an ST7036 for which F. Malpartida had an Arduino library. One of the Particle libraries also mostly worked if you told it the display was an OLED but that then assumed features an LCD does not typically have.