Manage prefix” allows you to populate all the Mobile number prefixes related to specific country and network operator. The list of prefixes against respective MCC-MNC is available as open source online or it can be provided by your gateway provider.
However, in order to identify that under which MCC-MNC, the prefix is falling you can navigate to Billing >> Master data manager >> Manage Prefix >> Verify prefix. And enter the mobile number to check under which network the mobile number belongs to.