From
http://androidforums.com/sprint-htc-hero/19422-ringer-lag-rings-other-end-few-times-before-ringing-hero.html#post128157
Perhaps I can try to bullet this:
* Call Sprint
* Ask for "Advanced Technical Service"
* Explain to them that you would like to change your Slot Index Cycle from '2' to either '1' or '0'
* Go to the phone dialpad and type in ##3282#
* After you hit the last '#' symbol, it's going to say "initializing"
* Next, it's going to want to know if you want to go into "view mode" or "edit mode"
Next steps require here the help of Sprint Support:
* Select "edit mode"
* It asks for a password
* Enter MSL number (must get from the Sprint representative)
* Go to the "Advance" tab in the "edit mode"
* Scroll down to Slot Index Cycle (it's going to be set to '2)
* Tap it and change it to '0'
* Once back in the "edit menu" hit the hard button menu button (next to the trackball) to bring up the save option to save your new settings
* This will save and reboot the phone