Class names like InvoiceReader, PriceCalculator, MessageBuilder, ArticleReader, InvoiceReader are not actually verb names. They are really “noun agent-noun” class names. See agent nouns.
A verb class name would be something like Validate, Operate, Manage etc. Obviously these are better used as methods and would be quite awkward as class names.
The biggest problem with “noun agent-noun” class names is that they can give very little meaning as to what the class actually does (eg UserManager, DataProcessor etc). As a result they are more likely to be bloated and to lose internal cohesion. (See Single Responsibility Principle).
Therefore the WebService class with the IInvoiceReader and IArticleReader interfaces is probably the clearer and more meaningful OO design.
This gives you the simple, obvious noun class name “WebService”, along with “noun agent-noun” interface names that clearly advertise what the WebService class can do for callers.
You could probably also give more meaning to the actual class by prefixing another noun, for example PaymentWebService.
However the interfaces are always better than a single class-name at describing more specifically what the class can do for callers. As the class grows more complex, new interfaces can also be added with meaningful names.