I purchased a item for my pet from an online retailer a few weeks ago. After a few weeks of normal use, I noticed that the material had become damaged. I sent the retailer photographs of the damage and they asked me to send it back to them for an 'investigation'. They received it back and said it looks like my pet has damaged it by chewing or biting it, even though my pet has never had the opportunity to do so - it is stored away from them. They suggest the dog has chewed on it even though there no obvious teeth marks (and I know 100% he hasn't), but they describe things like how there is a small indent in the material as well as the damage, which they have said is from a small tooth (?) The retailer says they have never seen damage like this before and their products are quality tested. I have reiterated that it has not been bitten. They do not believe me so have refused a refund/replacement.
Do I just need to accept their interpretation of what the damage looks like, even though it isn't true? I feel so frustrated.