When different type of programs are developed one wants to make these adjustable to future changes and requirements. It must be done a good design of the program from the beginning to make it possible to continue development of it without having to redo big parts of it to high costs. In the area of object orientation there are design pattern, which can be used to design systems that can be adjusted to new changes in an easier way. I have in this thesis chosen to take a closer look at how to design a program that sends SMS to cell phones through a system of an operator. One requirement on the program is that it has to be possible to change what operator to send though in an easy way. I have chosen a design pattern named Bridge and investigate if a use of it makes a program operator independent. This thesis is for system developers who have basic knowledge of object orientation and have programmed in Java. The hypothesis that is tested is: "If the design pattern Bridge is used to construct a program that sends SMS, then it will be a program where an operator's API easily can be replaced by another operator's API. The investigation was done by collecting a number of API's from different companies who offer the possibility to send SMS through themselves. Code was created for the classes that are part of the design pattern Bridge and specific code for every tested API were done and compiled and run. After that the possibility to switch between API's in an easy way was investigated. The result of the investigation was that it is possible to integrate some of the API's with Bridge and that the switching between API's is working. But to find out if Bridge can be used in a real program demands further investigations.