Hi!
There are two types of CHAR variables: signed char & unsigned char. Signed char is 7 bit long+1 bit of sign. Unsigned char is 8 bit long. As you can see signed char range is from -127..+127, unsigned char from 0..255. What is you variable type?
Next (very important) is the mode of your UART. You should use mode 2 or 3 which means "9-bit UART". What is your UART mode?

Regards,
Jacek