Why doesn't my Passport SMS config show Service Center Address?

Hello, I'm on a BB Passport, OS 1.3.2.2639 - Radio 2640.

I can receive SMS but I cannot send them. I have tried the regular troubleshooting for this that suggest to enter/re-enter the message centre number the phone company provides in the field "SERVICE CENTRE ADDRESS", usually located at the Advanced Menu of the Text Message Config.

I emphasize "usually" because in my case such a field (the Service Centre Address I mean) does not exist.

Any idea out there?

Thanks