(See I'm not joking about being really really old )
They'll ask you what they need to know. Most will have a script or a set of forms to fill in.
The key piece of information is your clearing number (that gives them access to your entire application, grades PS reference the lot) and what courses you're interested in (and if you have any flexibility over subjects). They might also ask for grades up front (there's no use asking for your clearing number if you got EEE and are enquiring about a ABB course.
You're a girl?! I assumed you were a bearded male in their mid-35's. Green eyes, brown hair, maybe be-specticales with a posh middle class accent.
Say the clearing req's is ABB, is it pointless to try with BBB?
If the standard offer on their website is ABB then call.
If they have clearing offers on their website at ABB (ie they have different offers for clearing on their website) then you can still call but be prepared for a no.
I'd always recommend starting off your phonecalls with a dead cert. It'll make any later knock backs easier to deal with.