I made three mistakes today for my Nav4 to Penang. First mistake, I did not hear the instructions given by the tower. Second, I did not ask the tower to repeat the instructions again as it is my responsibility to make sure I understand what clearance that I was given. Lastly, I did not follow the instructions given.

Here was what happened:

I was holding at Holding Point Charlie. After perform all the pre-takeoff checks, I requested for air traffic clearance (ATC).

Me: MAHA ***, request for ATC.
Tower: MAHA ***, cleared for NAVEX4 as per flight plan, 4000ft, squawk code 3111.
Me: Cleared for NAVEX4 as per flight plan, 4000ft, squawk code 3111, MAHA ***.

Me: MAHA ***, is ready at Charlie.
Tower: MAHA ***, line-up runway 21, cleared for take-off, right turn, cleared initially west of airfield, 4000ft.
Me: Line-up runway 21, cleared for take-off, right turn, 4000ft, MAHA ***.

#Notice what information I left out???#

I line-up runway 21, and straight take-off. After 500ft I made a LEFT turn. Suddenly the tower called me,

Tower: MAHA ***, what was my clearance given to you?

I was like stunned a little. Did I do anything wrong somewhere? Thinking back the clearance given. So I said:

Me: Cleared for takeoff, maintain 4000ft, MAHA ***.

There was another traffic (my friend) who also just took-off a minute before me on the same route to Penang. So the tower asked him the same question. My friend was not listening to the clearance given to me. So he just repeated what I said. Then.....

Tower: You all are not listening to what I said, is it? MAHA ***, cleared for finals runway 21, after landing, come straight up to tower!
Me: Cleared finals runway 21, after landing, proceed to tower, MAHA ***.

At that point of time, until I landed, I was still wondering where I went wrong. It was only when I came out from cockpit I realized that I made the opposite turn to what was told by tower. SH*T. I went up to the tower to meet with the tower staff after I parked the aircraft. I thought he was going to scold me. But, I was wrong. He told me where I went wrong, and gave me some advice regarding the RT do's and don'ts. And of course, I am grounded for today, he said, sort of like a punishment. Haha. I have already informed the Flight Ops about my situation and hopefully they will arrange me to fly tomorrow.