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.