Wrong php.ini being read at my hosting account

When I log into my hosting account I have access to the official phpinfo() script and it shows certain extensions (like mbstring for example) as available, but they are not available to my scripts. Every time I try to use them I get "Call to undefined function" errors. At first I just avoided those extensions but now I really need the mbstring extension so I started looking for solutions to this problem. I realized that my phpinfo() script gives a different output than the official one, and I think it's because it's showing a different path to php.ini. My script shows /usr/local/lib as its php.ini path and the official one shows /etc/php4/apache. So, after reading some of the older messages on this list I tried putting "SetEnv PHPRC /etc/php4/apache" in my .htaccess file. Then, my script was showing that as its php.ini path but it was obvious it was still giving the same output. I also remember (from the archives) someone else said his phpinfo() was showing the same path, but he said there was no php.ini file at /usr/local/lib on his system. And all I remember from his thread is that php is probably just using the default settings and showing /usr/local/lib as its path. I don't know if there is a php.ini on their system at that path or not, all I want to do is use the extension the hosting company is showing as available in it's phpinfo() script. I've tried contacting them, but they have given me some really stupid answers (free hosting, that's kind of what I expected). I think it's also important to point out that this it the first time I've opened a hosting account so I'm not really sure if this is their problem or mine. Shouldn't both phpinfo() scripts give the same results? Any help would be really appreciated.