Really poor customer service iPhone 3G

I have been a fan of apple sice I was 8 years old and have spent over £10,000 in total on apples products.
Here is a list, in chronological order of the events which have lead to my utter dismay with apples recent customer service:
My son glues headphone jack into socket
Apple tell me on the phone they can repair it
I arrive at apples store and am told they cannot repair it
Apple recommends I send my phone to my insurance company
Insurance company repairs headphone jack and returns it to me
I get scratches on my screen
Apple tell me on the phone they can replace my screen
I arrive at apples store and they replace my screen
New screen cracks while my son is playing a game
Apple tell me on the phone they can replace my screen
I send my iphone to apple
Phone comes back with a note to say it is beyond economical repair as the insurance company opened my iphone.
I have been extremely unimpressed with apples response on this matter and am posting this here to raise awareness about the poor customer service apple is providing to long standing customers at the moment.
Simple questions that I feel deserve simple answers........
How can apple say they wont replace the screen as my phone is Beyond Economical Repair after apple already replaced it at their store?
If apple are admitting that the servicing of my phone at the apple store was a mistake, why are they not willing to rectify that mistake and repair the faulty screen they installed mistakenly?
I intend to become apples worst nightmare until they resolve this issue.
Iphone 3gs iOS 4