public static async Task <Result <string> > VueBalance(this SmsClient smsClient)
        {
            var response = await smsClient.GetAsync("sms/admin/v1/contracts");

            if (response.code == HttpStatusCode.OK)
            {
                return(new Result <string>(true, string.Empty, response.result));
            }
            return(GetError <string>(response));
        }
        public static async Task <Result <string> > GetPurchaseHistory(this SmsClient smsClient)
        {
            var response = await smsClient.GetAsync("sms/admin/v1/purchaseorders");

            if (response.code == HttpStatusCode.OK)
            {
                return(new Result <string>(true, string.Empty, response.result));
            }
            return(GetError <string>(response));
        }