No busy signal

[batchen]

Hello i have an issue with Yealinks (Yealink SIP-T22P FM 7.72.18.5 )
our compeny have only 3 yealinks and the rest is Grandstream.

for some reasone the Yealinks does not give us a busy signal if im calling to
a busy phone number (like somone is allready on the phone) or if there is a music instad of a ring tone in some numbers we do not hear them.

we hear a regular dial tone.

can you please help?
somone reccomended me to change Early media setting so i did from disable to enable and it did not help.

any idias?

Regards,