   Fetches the label for `shipment` for a specific `Service`. The `service`
   module contains the `Carrier` and selected delivery speed.
 
-      Shippex.fetch_label(shipment, service)
-  """
-  @spec fetch_label(Shipment.t, Service.t) :: {atom, Label.t}
-  def fetch_label(%Shipment{} = shipment, %Service{carrier: carrier} = service) do
-    Carrier.module(carrier).fetch_label(shipment, service)
+      Shippex.create_transaction(shipment, service)
+  """
+  @spec create_transaction(Shipment.t, Service.t) :: {atom, Label.t}
+  def create_transaction(%Shipment{} = shipment, %Service{carrier: carrier} = service) do
+    Carrier.module(carrier).create_transaction(shipment, service)
   end
 
   @doc """

      Shippex.env #=> :dev
  """
  @spec env() :: atom
  def env do
    case Application.get_env(:shippex, :env, :dev) do
      e when e in [:dev, :prod] -> e
      _ -> raise InvalidConfigError, "Shippex env must be either :dev or :prod"

      Shippex.carriers #=> [:ups]
  """
  @spec carriers() :: [Carrier.t]
  def carriers() do
    cfg = Shippex.config()

    ups   = if Keyword.get(cfg, :ups),    do: :ups
