That's a real pain, eh? The dairy splits when it freezes, which is what gives you that weird texture. The easiest way to deal with it is to freeze your soup base without any cream or milk in it. Then, when you're reheating it on the stove, you can stir the cream in at the end.
If you've already frozen a batch and it's separated, you can usually save it. Just heat it slowly and give it a good whiz with an immersion blender. That should bring the creaminess back.