Student Reward not paying out

After a few months of struggling to get the student reward card posted to me, we finally gave up and decided to pay it directly into my bank account. Then on the 23rd of Nov I saw them paying money into my account, only to recall it on the 24th Nov. So I gave them a call asking about my student reward benefit and the outstanding amount - They now don't know anything about the outstanding sum. They have however on the 20th payed out a smaller amount, but not the total amount. Somehow all the money accumulated over a 2 year span is now gone, not nice!