I've always had great luck dealing with that supplier, have you tried the sample program they put on ebay itself?
//int ADDR = 0x27;
int ADDR = 0xA7;
byte x = 0;
byte data = 1;
LCDI2C4Bit lcd = LCDI2C4Bit(ADDR,4,20);
Wire.begin(); // join i2c bus (address optional for master)
lcd.printIn("I2C 1602 LCD");