are fdatool generated filter coefficients reliable or they still need to be converted in some other form?

I want to design a filter to remove 300 to 3300 hz frequency from audio clip.for that i ll imply a high pass iir filter and than a low pass iir filter.I want implementation in c,so would need filter coefficients generated from Matlab. how i decide order of filter? are filter coefficients generated from fdatool in z domain? bcoz coefficients generated are not giving me correct filter result in c

[Honglei Chen]

Could you elaborate what you mean by the coefficients not giving you the correct result?