connection or just bad luck

[savageman25]

here we go again i hear you say.
i just wanted to no if any of you ooplets know what them market people do when you take a phone to them and they change the phone so that it can go on any network, because all the phones that i have taken to them (about 6 of them) have all had to be peplaced becasue the screen has broken, the other phones that havent needed to be unlocked to other networks seem to be alright and i was just wondering if you think its the stuff that they get unlocked with some how damages the screen or if its just bad luck.
When i say damage the screen i mean that when you turn it on the screen lights up but it just stays blue or white, everything else works such as the lights and sound just the screen wont display anything.
If anyone has any ideas on how to get it fixed please help me.