DTMF from NOKIA phone not detected

Hi all,

I'm making an IVR application, so any calls to my NOKIA60 phone are answered by the IVR mode.

I tested it with ordinary home phone, it is okay...no problem at all....but when I tested it from NOKIA6670 and NOKIA6680, it doesn't work !!!!
I'm using the GOERTZEL method -> record first, analyze and then decide which tone is pressed

Is key-pressing at house phone and NOKIA phone different?

thank you,

irma