webmethod asynchroized call

Hello Developers,
We are using SAG web methods. The issue we are having is calls are synchronized. When two clients (a & b) applications calls same method, a has to wait for b’s request to be satisfied before a’s request is satisfied. How can we make these call asynchronized?

Generally calls are multi threaded if two different threads invokes the Same Method. Not sure how you are saying it is synchronized.
Take the thread dump and see thread ids. If two different ids then it is parallel execution only.
Are you invoking APIs via External Port?