I switched a monthly Tmobile plan several months ago and absolutely hate the voicemail "service". I previously had all my VM's sent to my email via YouMail (kind of like Google Voice).
Today while looking through settings I noticed there are three Voicemail Forwarding numbers in the Phone Settings menu. Each for a different scenario (busy, unavailable, unreachable). All numbers are currently set to Tmobile's VM handling number.
Has anyone with a TMobile monthly plan had success in changing these numbers to use a third party VM service such as Google Voice or other?
At the suggestion of a forum member elsewhere, I called TMobile and asked them about their new "uncarrier" plan. It is a non-contract, postpaid plan with the exact same pricing and services as my current TMo prepaid plan, but I regain the ability to forward voicemails among other things. You have to submit to a credit check for a possible deposit (max is only one month's plan ie $50).
So going to the "uncarrier" plan was the solution for me. Hope this helps.