IKEA Refuses to Replace My HOVAG Mattress Despite 25 Year Warranty

I purchased a HOVAG brand mattress with service code 30244389. Although it comes with a 25-year warranty, the mattress has developed a noticeable dip and collapse. An IKEA customer service representative inspected it and mentioned that repairs are covered for up to two years. He stated that he could approve an exchange but did not have the authority to do so, so he took photographs and sent them to the main office. Later, I was informed that the issue was considered a user error, and their suggested solutions were always the same. I was even told not to lie down on that specific spot. If there is a dip, am I supposed to fix it with my hands every time? I would appreciate your assistance with this matter.