/// <summary>
        /// Allocate toll free number and assign it to the application
        /// </summary>
        /// <param name="phoneNumber">IPhoneNumber instance</param>
        /// <param name="availableNumber">IAvailableNumber instance</param>
        /// <param name="applicationId">Application Id</param>
        /// <param name="name">Name of allocated phone number</param>
        /// <param name="cancellationToken">Cancellation token</param>
        /// <returns>Created phone number</returns>
        public static async Task <string> CreateTollFreeAsync(this IPhoneNumber phoneNumber, IAvailableNumber availableNumber, string applicationId, string name = null, CancellationToken?cancellationToken = null)
        {
            var query = new TollFreeNumberQuery {
                Quantity = 1
            };
            var result = (await availableNumber.SearchAndOrderTollFreeAsync(query, cancellationToken)).First();
            await phoneNumber.UpdateAsync(result.Id, new UpdatePhoneNumberData
            {
                ApplicationId = applicationId,
                Name          = name
            }, cancellationToken);

            return(result.Number);
        }
 public Task <AvailableNumber[]> SearchTollFreeAsync(TollFreeNumberQuery query, CancellationToken?cancellationToken = default(CancellationToken?))
 {
     throw new NotImplementedException();
 }