I think this really depends upon the value you placed on your relationship with Elan; and, the value you place on your time.
Calling the general line will likely yield no results as this is not within the purview of the typical center rep. Your best bet is attempt to get in touch with their legal department.
Assuming that you find a person in the legal department that is willing to work with you and knowledgeable you still have two possible outcomes that will not change things: First is that you misunderstood what you did agree to; or, they did mistakenly pull and it can't be undone.
In the case of the latter you might be able to receive some compensation for credit law violation(s), with an out of court settlement. If they say "sue us", then you will have to show actual harm that occurred to you and you did not indicate an actual drop in credit score. Even if it did drop it might recover prior to receiving the loan, or it may not even make a difference. Mortgages are typically awarded in bands and anything above 740 qualifies for the best rates.
Even if you could show harm, IMO its unlikely that your suit would be successful. One would reasonable expect a hard pull when requesting a CLI. You are requesting the ability to borrow more and as such should expect a hard pull.
Add to this that a suit will probably cause ELAN to drop you as a customer so you will have to apply for new credit. This is likely to have a higher negative impact on your score, but I still doubt it will materially effect your ability to borrow or interest rate.
Have you actually talked to a lender?