Accelerometer calibration?

Hi everyone! First of all, sorry about my english, it´s not my matter language, i'll try to do my best. I have a question for you people.

I have recently bought an iPhone 3G, and, in some games that uses the motion (the accelerometer) like R.Racing GTI, Think Blue, Labyrinth 3D, I've noticed a slight uncalibration.

After that I installed some app's of spirit level (like A Free Level, and BLevelFree) and they says that the longest axis have a 5.5 degrees unbalance/uncalibration to the left (tested on a flat surface)
The other axes are a little bit unbalanced (about 2 or 3 degrees)

I've asked in my mobile phone provider and they said to me that he can't change my iPhone for a new one because it's a problem of that external app's.
They says that the "official" Apple test for the accelerometer is on Photos, Safari, etc. If they can switch 90 degrees the iPhone and the screen switch, then they consider that it's not an accelerometer problem.

I've read other posts about the same issue, but I could'n find a concrete response.

I want to know if really there is no problem with my accelerometer, because the 90 degrees switch works fine, but not in the games that uses the accelerometer. It's a bit uncomfortable to try to play that kind of games.

Does the mobile cell provider should change my phone?

Apple does not care if this uncalibrated accelerometer 5 degrees?

Why there is no a settings button to calibrate the accelerometer?

What should I do?



*Thank you very much for your time and your answers.*