Hello! I believe you will need to talk to T-Mobile about it to have it switched, keep in mind, some of the plan charges change as well, so please ask or look into this when you bring it up. Now, if you take no action regarding this news, nothing will change and you will still receive the same plan/service/price as you were. You should be able to just chat with an agent, and make sure to ask and clarify what will change in your bill (make sure its not extra).
Resources:
- TMONews Article: Source
- Contact Us
Let me know if you have any questions/comments!