While working on creating some new ringtones for my iPhone, I realized from looking at ringtones for other phones that they varied wildly in length, music could be 30 seconds or more, and short clips might be only a few seconds. From past experience, I knew that my phone would only ring about 4 times before going to voicemail, and that this wasn't 30 seconds, so, how long should I make my ringtones for maximum effect?
After some digging online, it seems that the phone carrier controls how long your phone rings before going to voicemail, and that this option can be changed through some cryptic codes.
Doing the Query above, I found that my delay was currently set to 20 seconds before going to voicemail. This delay can be set to a number from 5-30, in 5 second increments.
The destination above is the number your phone uses get to your local voicemail system, it will be +1, followed by your area code, followed by the 7 digit local voicemail number.
What exactly the *11 does, I have no idea, and some guides have this parameter omitted, so you can try it either way.
To cancel forwarding completely (no more calls going to voicemail, use the Cancel command above.
So, armed with this info, you should now be able to create your own ringtones of an appropriate length, and set your delay to match your ringtones a bit more closely.