Operation maintaince cannot be

ORA-14048: a partition maintenance operation may not be combined with other operations
ORA-06512: at "EMACH.ADD_PARTITION_CDR_MONTH", line 19
ORA-06512: at line 1

While creating the table a default partition and subpartiton was created

This is the procedure that i have created to include the partitons and subpartitons.

CREATE OR REPLACE PROCEDURE Add_Partition_Cdr_Month
IS
IDATE DATE;
INPUTDATE DATE;
NDATE VARCHAR2(100);
INPUT VARCHAR2(100);
Res1 NUMBER :=0;
testid table2.rcp_id%TYPE;
CURSOR c1
IS
SELECT DISTINCT (rcp_id) FROM table2
WHERE snd_id IN (SELECT DISTINCT opt_owner_id FROM CFG_T WHERE opt_id = 8 AND opt_owner_id <> 'ALLOP') AND ra_sts IN ('P', 'L', 'T') AND
(ra_end IS NULL OR ra_end < SYSDATE) ;
BEGIN
SELECT LAST_DAY (SYSDATE)+1 INTO IDATE FROM dual; --- 1st june
SELECT ADD_MONTHS (LAST_DAY (SYSDATE)+1 ,1) INTO INPUTDATE FROM dual; -- 1st july
NDATE := TO_CHAR(IDATE,'YYYYMMDD');
INPUT := TO_CHAR(INPUTDATE,'YYYYMMDD');
EXECUTE IMMEDIATE 'ALTER TABLE table1 ADD PARTITION CDR_'||NDATE||' VALUES LESS THAN (TO_DATE('||INPUT||',''YYYYMMDD'')) (SUBPARTITION CDR_'||NDATE||'_000000 VALUES (''00000'')) TABLESPACE S_mem2_D';
FOR testid IN c1
LOOP -- check if subpartition exists
SELECT COUNT(*) INTO Res1 FROM all_tab_subpartitions WHERE subpartition_name LIKE 'CDR_'||NDATE||'_'||testid.rcp_id; -- create subpartition
IF Res1 = 0 THEN
EXECUTE IMMEDIATE 'ALTER TABLE table1 MODIFY PARTITION CDR_'||NDATE||' ADD SUBPARTITION CDR_'||NDATE||'_'||testid.rcp_id||' VALUES ('''||testid.rcp_id||''') TABLESPACE S_mem1_D';
END IF;
END LOOP;
END;