ThreadAbortException when Task calls method in service reference

Question

I need to call a method in a Service Reference with the name CancelTransactionByRefPos. This method has the following signature:

int CancelTransactionByRefPos(long refPos, out string resultDescription);

If this method returns '0' the cancel is succeeded. If this method returns another value, the method has to be called again.

I have written a Cancel method which calls the CancelTransactionByRefPos. It is very important the call happens asynchronous because it can take 30 seconds till a response is given.

My method looks like:

public void Cancel(long refPos, GiftCard giftCard, Account_3_2 account)
    {
       var task =  Task.Factory.StartNew(() =>
        {
            int result;
            do
            {
                string resultDescription;
                result = _client.CancelTransactionByRefPos(refPos, out resultDescription);
                // logic to log the result with the giftcard and account parameter
            } while (result != 0);
        });
        // task.Wait(); // ######## Uncomment this -> code executes! ######## 
    }

When I Cancel with the task.Wait() part in comment, I get a ThreadAbortException.

When I uncomment the task.Wait() and execute again, everything is doing well but if I have to wait until my task is executed, there is no use calling the method asynchronous.

EDIT

I have also configurated the service reference so it allows generation of asynchronous operations. Same problem.