Been told that Silicon phone case isn't covered by a warranty even though its only 5 months old?

FWIW ...

While Apple might consider this normal wear and tear, your next step of visiting the local Apple Store could be a good move. Sometimes, in-person conversations with a manager or staff might yield a more favorable result, especially if they can physically inspect the case. Bringing up the fact that you’re using it in typical conditions and not subjecting it to harsh environments could help your argument.

Some users have reported mixed experiences—some getting replacements in-store despite similar denials via online support. It's definitely worth giving it a try!

Just to be aware, silicone products, like cases or accessories, are generally more prone to certain types of wear and tear compared to materials like leather or hard plastics. Silicone tends to be softer and more flexible, which is great for shock absorption, but these properties also make it more susceptible to tearing, especially in areas with frequent use or stress, such as near charging ports or buttons. Over time, silicone can also degrade when exposed to oils from your skin, environmental factors, or regular wear.