A method for a mobile station, the method being for transferring deferrable data in a wireless communication system, the method comprising: receiving an instruction to transfer deferrable data, wherein the deferrable data is data of a first priority; and determining whether or not an air interface is too congested to allow transfer of data of the first priority; and wherein the method is characterized by: when it is determined that the air interface is not too congested to allow transfer of data of the first priority, generating and conveying a request to initiate a data call to transfer the deferrable data as data of the first priority, the request to transfer the deferrable data as data of the first priority including a first Service Option value indicating the data call being a deferrable data call associated with data of the first priority; when it is determined that the air interface is too congested to allow transfer of data of the first priority, generating and conveying a request to initiate a data call to transfer the deferrable data as data of a second priority, the second priority being a higher priority than the first priority, and the request to transfer the deferrable data as data of the second priority including a second Service Option value indicating the data call being a traditional data call associated with data of the second priority; and negotiating and establishing (414, 428) the data call in accordance with the corresponding Service Option value. receiving an instruction to transfer deferrable data, wherein the deferrable data is data of a first priority; and determining whether or not an air interface is too congested to allow transfer of data of the first priority; and wherein the method is characterized by: when it is determined that the air interface is not too congested to allow transfer of data of the first priority, generating and conveying a request to initiate a data call to transfer the deferrable data as data of the first priority, the request to transfer the deferrable data as data of the first priority including a first Service Option value indicating the data call being a deferrable data call associated with data of the first priority; when it is determined that the air interface is too congested to allow transfer of data of the first priority, generating and conveying a request to initiate a data call to transfer the deferrable data as data of a second priority, the second priority being a higher priority than the first priority, and the request to transfer the deferrable data as data of the second priority including a second Service Option value indicating the data call being a traditional data call associated with data of the second priority; and negotiating and establishing (414, 428) the data call in accordance with the corresponding Service Option value. when it is determined that the air interface is not too congested to allow transfer of data of the first priority, generating and conveying a request to initiate a data call to transfer the deferrable data as data of the first priority, the request to transfer the deferrable data as data of the first priority including a first Service Option value indicating the data call being a deferrable data call associated with data of the first priority; when it is determined that the air interface is too congested to allow transfer of data of the first priority, generating and conveying a request to initiate a data call to transfer the deferrable data as data of a second priority, the second priority being a higher priority than the first priority, and the request to transfer the deferrable data as data of the second priority including a second Service Option value indicating the data call being a traditional data call associated with data of the second priority; and negotiating and establishing (414, 428) the data call in accordance with the corresponding Service Option value.