I have a generic program and this program need to interface with multiple sms service provider/application.

I am thinking of coming out with a generic web service/xml files for this application to grap. Is there any standard web service format that i can use? Basically, the content of this file are:
1. user name and password
2. Recipient number
3. content

I am not experience with web services and have started by reading some forums and articles. Any expert there, please help to advice. Thanks.