According to the ODA instructions for the Series 3:
- On the 'Thanks for using T-Mobile' screen, tap Next to continue. DIGITS will recognize that there is already an existing data paired with the DIGITS line.
- Select the number assigned to the previous device that you want to activate on the new Apple Watch, then tap Next.
Open the watch app on your phone, then click through to Pair New Watch (if your new device isn't listed here); then scroll down to select Cellular, choose Set Up Cellular, and then you will be directed to a T-Mobile page. Choose Next, then the next page should show that you have an Existing Data with Paired DIGITS Line. Select Next, then Close.
That's super sad the first one was broken but I'm glad you were able to get another one. Were you able to use the steps able to get the new watch connected? Please let us know.