Whom does the customer belong to? Where should the customer information reside to? Which is the primary IT system wherein the customer details are kept? Is the CRM the customer master? Is it the Billing? Is it the AR? Or is there the need for an independent IT system, exlusively oriented towards the customer details management? What about the so-called Customer Hub?
Imagine the case where a billing system must execute a billing cycle and produce invoices that will be sent to the customers. There is definately the need for a customer base to lie within the billing system.
For large Telcos with diversity in their activities there are customers that do not fall into the traditional telco customer category. For example, there are customers that may proceed with an one-off transaction with the Telco and for that transaction they should get an one-off invoice typically generated by an AR system.
Consider a consumer belonging to some other licenced operator (OLO) taking advantage of a merchandise offer that your telco launches (e.g. a cellphone or a fixed-line phone or even a modem/router). This is an one-off transaction that doesn't constitute a relationship. Therefore, a typical CRM should not be aware of this potential customer, not until it becomes one. But again, in order to build a relationship you most probably need an IT system to manage leads and opportunities, so bottomline you will need to keep the customer details in order to incorporate them into a lead & opportunities list. This is clearly a CRM task. And as such, it definately makes one think that CRM should be the customer master.
Now, consider for a moment that you are a financial telco guy. You don't give a penny for sales leads, offers and other commercial jargon. The only thing you want to know is the account balance of the customer, his debt, his credit worthiness. You most probably think that the world would be a better place to be, if there was a Financial hub that would maintain all customer financial transactions. And again, such a hub will have to somehow host and manage the customer entity.
Now, imagine that your telcos data are old; very old. They are initially born at those ancient times, where IT systems & business processes where subscription-oriented and the concept of customer was totally unknown; multiple unconsolidated customer instances spanning across multiple IT silos; poor data quality; insufficient customer feedback; synchronization problems; business analgesia; In this nightmarish case, you most likely need a customer hub that will consolidate all those sparse customer instances & keep this consolidation alive when a new customer instance is entered by the user, clean the customer data & keep them clean, apply rule-based modifications and propagate the changes towards the necessary IT systems according to pre-defined, business-originated criteria.
To conclude, traditionally, CRM is considered to be the customer master; and frankly it must be, this way or another. But legacy systems & processes impose the need for a customer hub. Such a hub, architecture-wise, is part of the CRM system. Or at least it should be.