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 (S618), 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 (S714), 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 (S813), 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 (S816) 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 (S618), 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 (S714), 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 (S813), 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 (S816) a process corresponding to the function relative to the communication device by the communication device . <EOS>