Poor performance on a right join

When doing a join query I am getting a responce time of 3 seconds. The
callhist table has 66000 rows and the phone table has 10000 rows. I
have an indexes on callhist.call_date, callhist.operator_id,
phone.phone, & phone.cust_code. Here's the SQL
SELECT a.CALL_DATE, a.OPERATOR_ID, a.CUST_CODE FROM PHONE as b right
join CALLHIST as a on (a.CUST_CODE=b.CUST_CODE) where (b.PHONE =
'555-555-5555') order by a.call_date desc;
The postgres db is running on a 2 P3 700 processor server with 1GB of
ram running Red Hat Linux 7.3. I am running PostgreSQL 7.2.2

Why is the query taking so long? What can I do to help the
performance?

Thanks in advance,

Carmen