SQL & PL/SQL :: Column Data In Rows

Currently I have a requirement where I need return data of different columns in rows.

For example: I have a table that contains monthly data for voice calls, sms count and mms count for each mobile. I will need to get the output as summary of voice calls, sms and mms counts in different rows. For this I am using an approach which I am not totally satisfied even though I am getting the required results (majorly because i am querying the table thrice for getting this data).

I would want to know about any alternate ways of implementation.

--Create table
Create table
UsageData
(Mobile varchar2(20),
CAL_MONTH Varchar2(20),
VOICE_CALL number(9),
SMS number(9),
MMS number(9)
);

--Data

insert into UsageData values ('9999','JAN',1,2,3);
insert into UsageData values ('9888','JAN',5,20,1);
insert into UsageData values ('9777','JAN',4,5,9);
insert into UsageData values ('9666','JAN',200,111,8);
insert into UsageData values ('9555','JAN',154,1534,3);
insert into UsageData values ('9444','JAN',0,2,212);

--Query

select 'VOICE_CALL' AS EVENT,sum(VOICE_CALL) AS UNITS from UsageData where cal_month ='JAN'
union all
select 'SMS',sum(SMS) from UsageData where cal_month ='JAN'
union all
select 'MMS',sum(MMS) from UsageData where cal_month ='JAN';