Methods and apparatuses are presented controlling access to a radio resource of a multi-subscriber identity module (SIM) user equipment (UE). For example, an example method is presented that includes initiating a call on a first subscription of the UE, and generating, during the call, a message for transmission to a network entity associated with a second subscription of the UE. Additionally, the example method may include starting a timer upon receiving the message at a transmission buffer of the UE. Moreover, the example method may include determining, upon expiration of the timer, that the message is pending transmission at the transmission buffer to the network entity, and transmitting the response based at least in part on determining that the message is pending transmission upon expiration of the timer. Responses may also be transmitted during inactivity gaps in the call.