iPhone rings twice and goes to voicemail

Hello JaneMelody.

Welcome to Apple Support Communities.

If I'm understanding correctly, your phone calls are ringing twice before being forwarded to voicemail, and you would like to extend that ring time. I will be glad to assist.

Do you have a cellular signal?

Have you tried restarting your iPhone? If not, give that try:

Restart your iPhone, iPad, or iPod touch

If the issue persists, I would recommend contacting your cellular carrier to check your ring time settings on their end.

Cheers.

One possible cause of that symptom is if you have call forwarding enabled in your Settings or on your account. But even if that isn't the problem it is a carrier problem; you need to contact your carrier's support.