There are probably several ways of doing it, but all will involve you synching your contacts with another service or application. It might be possible to import contacts in address book on a Mac (haven't tried as I don't have access to my Mac at work), or the M$ equivalent.
However, what I have tried is saving the spreadsheet with names and numbers as a csv file in Excel, and importing this file into Google contacts. I then have my Google account synched with my iPhone, so the contacts arrive in my phone.
Tiptopp