Hi,
It is fairly simple. It is as simple as b number table. In the tariff structure (for SMS), we define the codes.
For ex: If we got to allow SMS to STC – Saudi, we will define 96650, 96655 in the structure.
Now, if you want to block SMS to 966554 level alone, in the tariff structure define it like
966551
966552
966553
966555
966556 etc.,
Hope you got the point.