answer: #Person1# requests two wake-up calls from #Person2#, one at 7 and another at 7 thirty.
documents: #Person1#: Hi! I need to request a wake-up call for tomorrow morning.
  #Person2#: What time do you want the call?
  #Person1#: I need two calls, one at 7 and another at 7 fifteen.
  #Person2#: We can certainly do that. Expect a call from us at 7 o'colock and then again at 7 fifteen.
  #Person1#: Actually, can I change the latter wake-up call to 7 thirty. am?
  #Person2#: I can certainly do that. Is there anything else?
  #Person1#: I can't think of anything. If I do think of something, I'll be sure to call again.
  #Person2#: Okay. Good night, sir.