You need to carefully check your credit agreement, it may have a promissory note section which is the basis of your agreement, (eg loan, term, repayments, interest) whichever interest is quoted on the promissory note is what you've signed for, anything else may be just indications or loan information.
Also you should check if you opted for the payment protection to be included in the overall loan, this is not illegal but you'll have to read the policy documents to see if the policy goes down as the loan reduces (which you would expect)
Finally, if you think the credit agreement is fundamentally flawed then you could challenge it and take that risk. Or after careful examination write to the bank explaining how the document is flawed and see how they reply. Its very unlikely that it will be wrong because that could mean any loan written on that credit agreement is, however it may lead you to talking about a rate reduction.