Bad service on claim

I recently submitted a claim for my phone that was specified on our home insurance. Only once the claim was approved and paid did we realized it was not insured for the value we requested it for. I also did not recevie a revised schedule after the phone was added so I was not aware of the mistake. I'm now being told that it is my responsibility to ensure the amount is correct. I'm sorry, i have proof of the requested amount. I'm not responsible to ensure that you do your job. At no point did they offer a solution or compromise or even an apology for their mistake.