Entiendo
que
están
ocupados,
pero
esto
no
es
lo
que
pedí.
ehn-TYEHN-doh keh ehs-TAHN oh-koo-PAH-dohs, PEH-roh EHS-toh noh ehs loh keh peh-DEE
I understand you're busy, but this isn't what I ordered.
Leading with understanding ("entiendo que...") before your complaint is a respectful way to express frustration.