German phrase
Bitte melden Sie sich per ~.
Meaning
Please contact us by ___
When to use it
It asks you to contact us. The method is stated after "by" in formal settings.
Example dialogue
Bitte melden Sie sich per Post.
Please contact us by post.
In Ordnung, ich sende die Unterlagen per Einschreiben.
All right, I will send the documents by registered mail.