Just to add to the linguistic comments. "Zavolaj" is a singular imperative, plural would be "zavolajte". "blizkost" (or rather "blízkost") is a substantive and a better translation would be proximity (or closeness). Just so that you have some notion about the differences ... in Czech it would be "zavolej/zavolejte" and "blízkost" :-) And that's rather the norm, not an exception.