Hello, its simple to implement that. I'm willing to give you the info for free. There are two ways, the first way works for every provider but usually leaves a missed call because the phone has to ring for one second. It works by making two simultaneous calls and quickly hangup the first call, the second call will be send to voicemail because the line was busy. That doesnt work if the subscriber has call waiting ON. The second and best way is to call directly the voicemail number of the network provider, some providers have a voicemail number in this format, eg T-Mobile Netherlands +31624(subribersnumber) and other have a universal one, to get into the voicemail of a specific subscriber using the universal voicemail number, you need to "lie" that the call has been forwarded by the subscriber you want to send the voicemail to, with asterisk this can be done like that exten => n,,Set(REDIRECTING(from-num)=here goes the number of the subcriber) , exten => n,Set(REDIRECTING(reason)=unavailable) , and the exten => n,Dial(and the voicemail number of the provider). Hope this helped you.