Calls not being forwarded to the Gear S2

Hi. Ive just added the wearable plan to my account, but calls are not being forwarded to the Gear S2. I have set the option in the app on my S7 Edge to forward calls when remotely connected. Here is a summary of what happens:

Devices connected via bluetooth: When I call my phone line, both the phone and Gear S2 ring, and I can take the call from either

Gear S2 in standalone mode: When I call the Gear S2 number, the watch rings

Devices remotely connected (bluetooth on phone switched off): Gear S2 says it is remotely connected, and that calls are being forwarded. However, when I call my phone line, only the phone rings rather than the Gear S2

Can anyone help resolve this issue? Both the app on my phone and the Gear S2 have the correct number for the watch. I have logged the problem with T-mobile and so am waiting for tech support to get back to me. It seems unlikely that this is a problem with the device since everything else works, and is more likely to be a network issue

Thanks