Apple TV+ activation verification code SMS not received

Apple TV+ Subscription activation requires a 4 digit verification code send via SMS (no other options) to the associated phone number. That SMS is never received.

This is the last step on activating the subscription when linking to the T-Mobile benefit.

No, the problem isn't at T-Mobile, SMS's from them work fine as do two factor authentication codes from Apple to this same number. Only this verification code SMS seems to never arrive.

I've tried this linking and unlinking now about 10 times over a 3 month period and been going this through with T-Mobile also multiple times as they're invoicing me on a benefit I can't use.

Any ideas / suggestions from the community or should I just give up?