'Always Trust' wifi network not working
From your description, one of two things is likely happening.

Here's what's supposed to happen, your IT department should package the certificates you need to "trust" their servers and networks and they should provide them and hopefully not change the certificates every few weeks or months. Better, they could pay for a real certificate that's signed by a trusted broker and your Mac would just know it was a valid certificate and not just something the IT department self-signed.

Your Mac should take the certificate needed and enter it into your keychain when you tell it to "always trust" the certificate, but that isn't working as well.

So - you could troubleshoot your keychain (start with the help menu in keychain access program) or learn more about how that works. You could ask IT to point you to the actual certificates and learn how to store them in your keychain or the system keychain. You'll want to run the Certificate Assistant from Keychain Access if you choose to store the certs locally since it will help you know if you have a good chain of trust and to debug things, since this usually takes several tries if you're not in the habit of installing custom certs into OS X.