Dual Sim Voicemail setup issues

I recently setup an additional phone number on my iPhone 11 pro for my business. I wanted to share some challenges I had and my resolution.

Carrier: T-Mobile

Phone: iPhone 11 Pro

Issue: Visual Voicemail Greeting not showing both accounts

Details: Clicking on Visual Voicemail and the Greeting button shows "To change your voicemail greeting first select an account". Only one of my accounts is listed.

Solution:

1) Dial 123 from the account that isn't showing up on the custom voicemail screen (if you don't know how to do this, click on Keypad and at the top you should see your primary account, if you click it, you should be able to choose your different account to dial the call from).

2) Setup custom greeting from your prompts.

3) Go back to visual voicemail and you'll see under greetings your other account listed.

4) If you try to go to the second account and record a greeting you will get an error (com.apple.mobilephone error 1035).

5) Reboot your phone

6) Dial 123 again from your account that wasn't working (same as step 1)

7) Choose custom voicemail and record a custom message (or select the existing one).

8) Go back to visual voicemail and your greetings, you should see both accounts and when you click on each one, they should show that there is a custom greeting that you can change separately now.

Now - I'm not sure if you can cut out some steps by rebooting your phone earlier, but this is what worked for me. I now have 2 custom voicemails, one for each line and I tested that they work. When I originally called T-Mobile, they had no idea on how to get this working so I will let them know as well.

I hope this helps someone.