what is the best server-web service- design(c#) for a mobile game

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C#

ASP.NET

webservice

Hello
I'm going to build a multiplayer game like "Clash of Clans" and other games like this.so I need a server(web service) to control the data and other processes but i cannot choose the best server design.

after some searching i found that the REST and SOAP may be perfect for me but i need a definite answer to choose one of them because i think changing from one to another is going to be difficult when the product is finished.

and i think my server is not going to process any graphic or complex content but just some strings and numbers and logs and XML and storing them in a database.

i would really appreciate it if someone could help me find my answer.