My IPhone 4 only rings 3 times before going to message bank
Which carrier? It can be done on AT&T, T-mobile . Not Sprint.
Verizon will, but you must call them @ 611.
For AT&T and T-mobile
Dial *#61# from your phone. Tap Send.
You should see a new screen that displays a bunch of information about what's getting forwarded. You should see a line under "Voice Call Forwarding" that says "Forwards to +11234567890" (where 11234567890 is an eleven digit phone number, likely different from your phone number). Write down this number and tap Dismiss.
Now, dial **61*+11234567890*11*XX# and hit Send, where 11234567890 is the number that you found in step two and XX is the number of seconds you want to wait until voicemail picks up. You can set it in increments of 5, where 30 seconds is the maximum.
After you hang up that call, you can have someone call your phone and see if it worked. On some phones, you can dial *#61# again and see how long it's delaying your calls, but our test phone (the iPhone) did not show this information.
Or call them.