Not receiving one time passwords/2FA via SMS after port to Telus

My wife and I no longer receive any 2FA/one time passcodes from Amex (and possibly other banks) whatsoever after porting our numbers to Telus (from Rogers) last week - same phone number but just a new carrier.

All other text messages and 2FA from other banks/ companies come through fine, except Amex.

Telus has concluded it's an issue with Amex since everything else is working fine, but Amex isn’t able to fix this either.