Because you don't have access to all the member variables of the classes and can't change this, you can't make SipService parcelable.
If you would have access, you could read all the variables of the classes in your SipService and make a new instance of them. But for that you need the getters and a appropriate constructor for each class to rebuild them.
If these classes are implementing the Serializable interface, you could make it serializable. Because it's behaving pretty much the same, but the performance is better if the class implements parcelable.
OR
If you can talk to the team, suggest them to implement the parcelable/serializable interface if it's a reasonable requirement.