Can't edit voicemail number V20 T-Mobile

[s.pearce88]

I can't edit the voicemail number on my T-Mobile V20. The option is greyed out. I was wanting to edit it so when i press 1 on my dialer , it will call my Google Voice. Does any one know of a way to edit the number ? As you can see from my screenshot it's greyed out. I am running stock , I'm not rooted

 

[Rukbat]

Ask in a TMobile store - they may have the number locked. (Then you'd have to program #2 [or any other number] as your GV number and use that.