A system described herein may provide an interface between a Session Management Function (“SMF”) and a charging system in a wireless telecommunications system. The charging system may generate triggers which cause the SMF to monitor traffic associated with user equipment (“UE”) and alert the charging system when certain trigger conditions have been satisfied. The triggers may be modified during a communication session between the UE and the wireless telecommunications system. The triggers may be configured on a per-subscriber or a per-price plan level basis. The SMF may also cache a number of satisfied trigger conditions before notifying the charging system, which may result in an efficient use of networking and/or processing resources. The unification of “offline” and “online” charging events, by virtue of the interface, may also result in an efficient use of networking and/or processing resources.