That's a false positive vs. false negative distinction too.
The GP is concerned that Tmobile allows hackers to impersonate you/your wife on the phone.
You're concerned that even after providing all possible account details - password, PIN, last four of her SSN, last bill amount, anything else they might want to ask that's not literally a live biometric scan - they can't distinguish the two of you just because you don't sound like a woman.
Perfection is unattainable.