how do i check my voice mail from another phone

Dial the number but that you want to check. After the message plays push the *. You will then be prompted to enter your passcode and press the # button. Your voice mail will then operate as if you were on the phone with all functions available to you. Hope that helps I just tried it myself out of curiosity and it works. If you don't have a passcode you will have to log on to your T-Mobile account and set up a passcode. 

But if you call the 805 number from another T-Mobile phone, it will automatically go into that phone’s voicemail.  Calling your own phone number, pressing *, and entering your PIN works ok.

this should be an easy one. dial 1-805 637 7243 and follow voice prompts to enter your T-mobile number and passcode.

I use all the time

You can also try calling your own number and when your prompt answers, press either * or #.

Most users don't set up a passcode when setting up VM.  It is not needed if calling to retrieve VM from your own phone when in U.S.

  The default code is the last 4 digits of your phone number.  It appears to be required even if you are using your own phone when out of the country.

‌so slick flaco

I just tried this but was not prompted to enter my passcode. When I pressed * it started recording. I tried calling back and pressing # and same thing. My phone is being repaired and it may take 2 weeks. Sure hope I can figure out how to get my VM somehow.

The answer I was looking for. Thank you. With four Tmoblie lines I need to check another one remotely and this solves the problem of going direct to the voice mail on the line you are using when you dial the 805 voicemail number.