Cannot dial extension with outgoing call

Hi All.

I’m sorry if this problem have been solved.

My PBX version is : FreePBX
All outgoing and ingoing call working just fine. No problem at all.

Till we find out that there is one unique case.

We try to call this number, called it : xxxx xxxx.
After we make a call, we arrived at their phone queue system, then we heard about which extensions we should press to proceed further. Here comes the tricky part. When we press the extensions that we intended, it cannot detect
number that we have pressed.

So what i try to do is that,

  1. I try to contact the same number using my mobile phone, and dial the extension It works just fine.

  2. Contact the same number, with land line phone, and it works just fine.

  3. Contact the same number, with different phone brand but same system, it doesn’t work.

This case only specifically when we dial that number. Maybe we haven’t found other case yet.

Can anyone help me with that?

Thank you.