1. A system comprising: a computing device comprising a processor; and a memory that stores computer-executable instructions that, when executed by the processor, cause the processor to perform operations comprising obtaining a routing scenario associated with a user of a routing service, wherein the routing scenario specifies customer data that is to be accessed when a call is received to determine a call handling decision, wherein the customer data is stored at a customer data source that is remote from the computing device, wherein the call is directed to a called device associated with the user, and wherein the call is received from the calling party, obtaining, from the customer data source and during the call, customer data that is associated with the calling party and with the computing device, determining, based on the customer data and during the call, the call handling decision, and providing the call handling decision to a network to route the call.