+=item customer_recurring HASHREF
+
+Takes a hash reference as parameter with a single key B<session_id>
+or keys B<agent_session_id> and B<custnum>.
+
+Returns a hash reference with the keys error, custnum and display_recurring.
+
+display_recurring is an arrayref of hashrefs with the following keys:
+
+=over 4
+
+=item freq
+
+frequency of charge, in months unless units are specified
+
+=item freq_pretty
+
+frequency of charge, suitable for display
+
+=item amount
+
+amount charged at this frequency
+
+=back
+