Maybe it depends on the country, but my memory of 2003 is almost every non-elderly adult I knew (in my own upper-middle class milieu) already had a mobile phone. Not a smart phone as we understand the term today, but a lot of phones back then had primitive smarts that are now largely forgotten, such as WAP/WML browsers (which maybe not many people used, but I certainly remember using one), JavaME applets (vaguely remember using them too-maybe post-2003, but higher end 2003 phones definitely could run them), vendor-specific mobile app formats such as Symbian