A communication system including a communication device, a first server system, and a second server system, the communication system comprising: a processing unit for executing (S615, S616) a process for receiving a user input indicating whether the second server system is allowed to execute a function regarding the communication device, based on an account link process for linking a first account for voice control with a second account managed by the first server system, a receiving unit for receiving, after the process for receiving the user input is executed, permission information indicating that a user has allowed the execution of a function relative to the communication device by using the first server system; a first performing unit for performing, after the permission information is received, a predetermined process for prompting the user to perform the account link process, in a case where a predetermined function that the user does not permit the second server system to perform is added as the function relative to the communication device; a second performing unit for performing, by the second server system, the function relative to the communication device that the user has, in advance, permitted the second server system to perform, in a case where an instruction for performing the function relative to the communication device that the user has, in advance, permitted the second server system to perform is inputted into a voice control device with a voice, after the predetermined process is performed and even in a state where the permission to perform the predetermined function by using the second server system is not obtained from the user; and a third performing unit for performing a process corresponding to the function relative to the communication device by the communication device. a processing unit for executing (S615, S616) a process for receiving a user input indicating whether the second server system is allowed to execute a function regarding the communication device, based on an account link process for linking a first account for voice control with a second account managed by the first server system, a receiving unit for receiving, after the process for receiving the user input is executed, permission information indicating that a user has allowed the execution of a function relative to the communication device by using the first server system; a first performing unit for performing, after the permission information is received, a predetermined process for prompting the user to perform the account link process, in a case where a predetermined function that the user does not permit the second server system to perform is added as the function relative to the communication device; a second performing unit for performing, by the second server system, the function relative to the communication device that the user has, in advance, permitted the second server system to perform, in a case where an instruction for performing the function relative to the communication device that the user has, in advance, permitted the second server system to perform is inputted into a voice control device with a voice, after the predetermined process is performed and even in a state where the permission to perform the predetermined function by using the second server system is not obtained from the user; and a third performing unit for performing a process corresponding to the function relative to the communication device by the communication device.