Ring back when hang up first from internal call to outsite

[briandang]

Hi Expert,
i have problem with can not solve at the moment.
my customer call out side than hang up first, and there will be a ring back. it quite unconfortable for my client. they do complain us.
i check with some engineer they told that because of busy tone can not detect and different OXO have diffrent busy tone detect. is this true? or we have to modify somewhere?
can any expert can help me to solve this problem.
and if can, can you sent me a busy tone detect software for OXO.

here is my email address : chuong@omnicomm.com.sg
your help is much appreciate.
i upload one sample of busy tone which i have from ALU software