A customer called a few weeks ago having some trouble managing the forwarding features on his iPhone. His cellular provider was not particularly helpful to him when he called for support, and he wanted to send his calls over to us at his answering service, so I did a little research in order to help him.
Our customer forwards his business line direct to his cell phone after hours. He wants to pick and choose which calls to answer, letting some forward to our staff here at Dexcomm while being able to answer his personal calls and the business calls he felt were particularly important, all the while never saddling any of his callers with voice mail. Direct forwarding from his iPhone to the answering service doesn't work because he doesn't get alerted to any calls.
After a few minutes on the phone discussing his concerns it became clear he needed to activate his "Forward, if no answer" feature so he could physically ignore calls and let them come to us (For many traditional carriers this service is called "Call Forward Don't Answer"). This is usually a simple process on traditional carriers because you just need to call up your phone company and ask them to activate the feature and tell them how many rings you want the caller to hear before transferring to the 3rd party number.