Hi david. Do you mean increasing the ring time before a call goes to voicemail? If that's the case, you need to contact your carrier directly to get the instructions. Or you can tell me which carrier you're with and I can find out for you.
Go to Settings, then Call Settings, then Call Divert, then Divert if no answer,hit OK, then Activate, then To Voicemail,should give a Wating time list. For Consumer Cellular the max wait time is 30 seconds. Select the wait time you want and hit OK. You will get an information screen showing your new wait time and the number you are forwarding to. Hit OK again and you are done and can back out of the settings menu. Hope this helps.