Default Edit Voicemail - Orange homescreen

Hi there,

I changed providers and need to know how to change the voicemail number on the orange homescreen's voicemail shortcut.

Thanks!

I also need to know how to switch from the orange home screen to the standard windows one, or toshiba's... I can't find the settings anywhere!
Phone: HTC Dream (G1)
Phone: Dell Streak
Phone: Galaxy Nexus
Phone: Samsung Galaxy Note
Phone: Nexus 4
Phone: Samsung Galaxy S3
Phone: Nexus 5
Phone: Samsung Galaxy S4
Phone: HTC One [M7]
Phone: Samsung Galaxy Mega 6.3
Phone: Sony Xperia Z1
Phone: LG G3 - Current

Tablet: HTC Flyer
Tablet: Samsung Galaxy Tab 7
Tablet: Samsung Galaxy Tab 8
Tablet: Samsung Galaxy Note 10.1
Tablet: Lenovo Yoga Tablet 8 & 10
Tablet: Dell Venue 8 Pro - Current