。
Could you wake me up at 7 tomorrow?
Literal
Tomorrow 7-o'clock [at-に] wake-up give-favor-not [polite-ますか].
~てくれませんか = 'won't you do me the favor of X?' — a polite request using negative question + くれる (give to me). Softer than ~てください because the negation implies the listener has the option to refuse. Typical polite hotel wake-up call request.