I'll be visiting Netherlands next month and i want to buy an iphone so as i understood i will have to sign a 2 year contract , if i did so and after a week i returned back to my country what would t-mobile do about it and what would be their reaction for such act ?? what would be the consequences for such an action ??? any legal problems and stuff ?????

Since you have a contract that says you have to pay for two years, the contract stands and you'd be liable to be sued becuase you're not holding up your end of a bargain.

Fleeing the country is never an option when it's crime.