A method for performing a communication service by using a plurality of modems, comprising: performing , by a first modem MODEM 1, a first communication service in a first frequency band; performing , by a second modem MODEM 2, a second communication service in a second frequency band, wherein the MODEM 1 and the MODEM 2 are in a first operating mode; receiving , by the MODEM 1 from an access network device, a switching instruction for the first communication service, wherein the switching instruction is used to instruct the MODEM 1 to switch from the first frequency band to a third frequency band; indicating , by the MODEM 1, to an arbitration apparatus that the MODEM 1 needs to be switched to the third frequency band; determining , by the arbitration apparatus, whether the third frequency band conflicts with the second frequency band, to obtain a determining result; and performing, by the arbitration apparatus, one of the following operations based on the determining result: maintaining the first operating mode, or switching the first operating mode to a second operating mode for the MODEM 1 and the MODEM 2; wherein the first operating mode is a concurrent operating mode, the second operating mode is a non-concurrent operating mode, wherein the concurrent operating mode is a dual SIM dual active mode, and the non-concurrent operating mode is a dual SIM dual standby mode, and the performing, by the arbitration apparatus, one of the following operations comprises: when the determining result is that the third frequency band conflicts with the second frequency band, switching , by the arbitration apparatus, the first operating mode to the second operating mode for the MODEM 1 and the MODEM 2. performing , by a first modem MODEM 1, a first communication service in a first frequency band; performing , by a second modem MODEM 2, a second communication service in a second frequency band, wherein the MODEM 1 and the MODEM 2 are in a first operating mode; receiving , by the MODEM 1 from an access network device, a switching instruction for the first communication service, wherein the switching instruction is used to instruct the MODEM 1 to switch from the first frequency band to a third frequency band; indicating , by the MODEM 1, to an arbitration apparatus that the MODEM 1 needs to be switched to the third frequency band; determining , by the arbitration apparatus, whether the third frequency band conflicts with the second frequency band, to obtain a determining result; and performing, by the arbitration apparatus, one of the following operations based on the determining result: maintaining the first operating mode, or switching the first operating mode to a second operating mode for the MODEM 1 and the MODEM 2; wherein the first operating mode is a concurrent operating mode, the second operating mode is a non-concurrent operating mode, wherein the concurrent operating mode is a dual SIM dual active mode, and the non-concurrent operating mode is a dual SIM dual standby mode, and the performing, by the arbitration apparatus, one of the following operations comprises: when the determining result is that the third frequency band conflicts with the second frequency band, switching , by the arbitration apparatus, the first operating mode to the second operating mode for the MODEM 1 and the MODEM 2. <EOS>