IPhone 3GS touch screen responds slowly or not at all since upgrade to 4.3.3

Question

Ever since my iPhone 3GS upgraded to OS 4.3.3, it behaves strangely.
The following happens from time to time, not all the time, but often enough to be annoying.
Reaction time of screen touches is slow or, worse even, when I touch an app (any app), it dims and then nothing happens, until I tap the screen on various spots, then the app where I pressed the last time opens up.
When typing a message or email, characters duplicate (not all the time).
When I want to delete ONE character, the whole text is deleted, slowly, one character at the time, and I can’t interrupt it.
When I want to scroll through screens, nothing happens….until suddenly multiple screens scroll by.
When I scroll down, like in Twitter, from time to time nothing happens or suddenly a tweet highlights all by itself (!!); when I try to continue scrolling down, that highlighted tweet opens.
When I close an app, it closes but the screen is not responsive (like above in #1).
I took off the screen protector.
I shut down and restarted several times.
I rebooted several times.
I restored the iPhone several times.
To no avail…..the same annoying and unpredictable problems pop up.
My mobile phone company (Orange) has no clue, though they suggest to “send it to Apple” which may take 6-12 weeks (!!!!).
The Apple importer in Israel (iDigital) has no clue and is not helpful at all: they claim they don’t handle iPhones.
Last, but not least: Apple doesn’t give any iPhone support either, not online, not by phone, nothing…..
Anybody can help?

Answer 1

No replies.....nothing from Apple, of course.
Update:
1. Orange had the phone for 2 days....and did nothing.....got it back in the same state.....claimed that there was "nothing wrong"
2. Meanwhile the iPhone was responding slower and stranger, opening apps by itself, disconnecting phone calls without touching the phone, freezing, impossible to scroll down (only up), impossible to answer phone calls because the screen wouldn't react......getting madder and madder
3. So with no "repairs", help or advice I did the whole rebooting and restoring bits again.... with ONE difference.... I restored first as a new phone and then again a second restore using my backup..... it took me almost 1 full hour........ BUT IT WORKED...... and I'm using the iPhone now as if it were brandnew..... the only setback is that you have to rearrange your apps from scratch, login your FB, Linkedin, Twitter, etc. anew, reload your pics and music, and in fact redo ALL your settings.... cost me 2 hours.
BUT COULDN'T ANYBODY TELL ME? 
APPLE????????