SMS to Mysql characters issues

Hi, i use Ethernet and GSM shield and i’m sending all received sms to mysql using GET php.
I have website where i can see all incoming sms and can reply/send sms from webpage.

The problem is, that everything works fine until i want to use extended ascii characters. When sms comes with letters like ąčęį everything goes wrong and nothing works. How can i use more then 126 acii codes?