Is to help you determine the carrier in SAS.
First establish if the call is an outgoing call or an incoming call
If the call is an inbound call the carrier is whoever owns the number check this by using numberview,
If the call is an outbound call we will use whatever carrier is cheapest and below will guide you how to find the carrier on outbound calls.
Outbound calls first grab the IP from SAS in some situations you may have to look at a few of them generally they are on the right side of the call as the originator for outbound will be on the left.
Second go to https://whois.arin.net/ and search for the Highlighted IP
Here we can see that the Carrier for the example is 382 communications