The paper is devoted to methods for identifying payment plans and services by mobile operators which are the best for the given subscribers. We base our research on the model-theoretic approach to domain formalization. We use Formal Concept Analysis for processing the mobile subscriber data. An Ontological Model of the domain “Mobile Networks” is constructed in the scope of this research. The Ontological Model of the domain is constructed by integration of data extracted from depersonalized subscriber profiles. The signature of this Ontological Model contains unary predicates which describe subscriber behavior and features of payment plans and services. We consider formal contexts where objects are subscriber models and attributes are formulas of predicate logic. We investigate concept lattices and association rules of these formal contexts. Knowledge about optimal payment plans and services for a given subscriber is generated automatically with the help of the association rules.