A wireless communications device includes a radio frequency (RF) module and a baseband chip. The baseband chip is configured to initiate a mobile originated (MO) call through the RF module with a first subscriber identity card when the RF module is occupied by performing a packet switched (PS) data service with a second subscriber identity card, arbitrate a first protocol stack handler to suspend or terminate the PS data service associated with the second subscriber identity card in response to initiating the MO call associated with the first subscriber identity card, and arbitrate a second protocol stack handler to make the MO call associated with the first subscriber identity card when the PS data service associated with the second subscriber identity card is suspended or terminated.