A wireless communications device is provided with a Baseband chip capable of coordinating operations between circuit switched (CS) and packet switched (PS) services with different subscriber identity cards. The Baseband chip is configured to receive a request for making a mobile originated (MO) call with a first subscriber identity card when performing a background PS data service with a second subscriber identity card. The Baseband chip suspends or terminates the background PS data service in response to the request, and further makes the MO call with the first subscriber identity card when the background PS data service is suspended or terminated.