I’m very new to all this so please be gentle with me!
I currently use a call forwarding service that receives calls to a virtual geographic number (my published business number), and forwards them onto my mobile, so I can answer my customers where ever I am. This service passes the on CLI from the originator, so I can see exactly who is calling.
I would like to use asterisk to replicate this facility add more functionality (an ip based pbx with several extensions through my premises), so that I can serve my customers better. I’ve got the theory sorted in my head, and I think it is achievable with asterisk - firstly I want asterisk to receive the incoming call (which will probably come in on a sip or iax trunk, along with possibly a single PSTN). Ideally I need it to answer and play a welcome message, before ringing the local voip handsets (possibly with some options - press 1 for X, press 2 for Y etc). If there is no answer on the local voip, I would like asterisk to forward the call onto my mobile phone via a GSM gateway (I have a Dinstar DWG2000).
But one big stumbling block (that might be a show stopper) in my mind, is passing on the originators CLI via the GSM gateway. Somehow I doubt that the Dinstar can do this - surely the network operator will use the GSM sim’s assigned number, and this is all I will see on my phone. So I will know that it’s a forwarded call, but can’t see who it is forward from? If I miss the call, and they don’t leave a message, I won’t be able to see their number to call them back.
Is my thinking correct on this? If it isn’t the case, then people would be malicously spoofing CLI all over the place. What, if any, work arounds are there that asterisk could handle? My first thoughts are putting the caller on hold while I answer the call and get asterisk to play a recording (or generate speech) to talk me the callers name or number. Is this practical or achieveable? The only other thing I can think of is to get asterisk to send an SMS with the callers number, but this would obviously be too slow to allow me to see who is calling before I answer.
Are there any other, more elegant/practical solutions, or am I stuck with using a voip service provider to achieve the cli forwarding? It must be possible as they are doing it themselves somehow. I am in the UK, in case that makes any difference?