Thanks for the quick answer.

I've done it with subsequent text yesterday.
After a software update I had to reinstall WhatsApp. Now I receive the error message: "... is no longer approved for our service". What happened and what can I do???

WhatsApp Support wrote:
Thanks for contacting WhatsApp. We are working on answering everyone's question as soon as possible. In the meantime, please look at our FAQ to see if your question is answered there.

So I think I have to wait and see what happens...