Singapore Airlines — poor audio-visual monitor on board

Dear sir/Madam

My wife and I flew back from Christchurch to Singapore on SQ298 on 1.6.18. Our given seats number were 33B & C.
Before we entered the aircraft, we were called aside to see the ground staff at the boarding entrance, the staff told us that the AV monitor of our seats were not working. She told us the crew member will talk to us and try to change the seats if possible.
After we had seated, one of the male crew member came to inform me that they had "did something" to the system and it should be working now. He also told me that the flight was full.

However I noticed the picture quality was so poor and the contrast was poor and I had difficulty to see the picture clearly. I told the crew staff that the set was not working properly and he asked me to let it run for a while. I also that only right side of headphone was working. He did not came back again.
I approached another crew staff and he tried to tilt the monitor and ask ed whether the picture was better, I noticed slight improvement but was not clear enough to enjoy the entertainment.
I gave out after a while as it was very tiring to squint the eye to watch the movie.
I noticed the aircraft was very old and poorly maintained.
Please respond to my complaint ASAP? Thank you.
From Dr Lim Chong Sing. P/H [protected]
Address: 35, Marine Crescent, #08-81, S(440035)
4.6.18