How to resolve persistent overheating issue on iPhone during routine tasks and charging?

Shortly after I started using the device, I noticed it began heating up significantly while charging. Since then, the phone heats up during routine tasks such as browsing, video calls, and even when idle. The heat is noticeable and concerning, making the device uncomfortable to hold at times.

I have already taken the following steps:

Visited an Apple Store, where a diagnostic test was performed. No issues were found.

Spoke to a customer support executive via phone. Unfortunately, the interaction was not helpful, and I was once again asked to revisit the store despite having already done so.

Given the recurring nature of the problem and the lack of resolution through standard channels, I kindly request that this matter be escalated to a senior support specialist or the appropriate department.

[Re-Titled by Moderator]