Did you already try to enter a phone number manually and send a text to it? For details of how that may help see here.
If you can still receive SMS you could ask your provider to resend the initial config SMS. Perhaps that does some fixing to the settings.
If not, you could ask your provider for the number of their SMS Center (SMSC). You can then check (or update) that number directly in the settings of some SMS Apps.
If not in the SMS App settings, you can enter that number in the test menu you should get when dialing *#*#4636#*#* - Phone info - SMSC.