To forward your voicemail back to your carrier's voicemail, please click the appropriate deactivation code (from your mobile phone) or follow the instructions below.

*Note: If the deactivation code doesn't work, please contact your carrier to reset your call forwarding.  Since your carrier controls the call forwarding, resetting it will revert the settings back to the carrier inbox. 

AT&T,  T-Mobile, and Rogers AT&T subscribers:

Dial ##004# then press [SEND]

Verizon subscribers:

1. Dial *73 then press [SEND]. You should hear a series of beeps and then your phone will disconnect. This is normal and it means that the feature activation was successful.
2. You may want to call your cell phone from another line to verify that your calls are now being forwarded to your Verizon voicemail.
3. If that does not work, you can also dial *710 then press [SEND].

Ref: http://support.vzw.com/clc/devices/knowledge_base.html?id=17268

Sprint subscribers:

1. Dial *38 or *720 then press [SEND]. You should hear a series of beeps and then your phone will disconnect. This is normal and it means that the feature activation was successful.
2. You may want to call your cell phone from another line to verify that your calls are now being forwarded to your Sprint voicemail.
3. If are unsuccessful, contact Sprint Technical Support at 888-211-4727 to disable call forwarding.

US Cellular subscribers:

US Cellular has different call forwarding access codes in different areas, please try which of the following works:
*73
*760
*740
*720

If none of the call forwarding deactivation worked, please call US Cellular at 1-888-944-9400 for instructions about deactivating Call Forwarding in your area. 

Metro PCS and Cricket subscribers:

Dial *740

Cellular South subscribers:

Dial *77