Paragraph 1 of DeleteSubscriptions says:

"This Service is invoked by the Client to delete one or more Subscriptions that it has created and that have not been transferred to another Client or that have been transferred to it ."

I wonder about the last part of that sentence "or that have been transferred to it"

If the above statement was correct then it would imply that the original client/session would have to delete the subscription, but we know that cannot be done because of the statement before it "...that have not been transferred to another Client..."

So the sentence seems to be at odds with itself. The structure of the sentence is misleading.

An easier to read sentence might be:

"This service is invoked to delete one or more subscriptions that belong to the Client's Session. Subscriptions that were transferred to another Session must be deleted by the Client that owns the session.