iPhone 16 Shuts Down Repeatedly, Service Delays My Device Without Updates

I purchased an iPhone 16 on September 23, and within a short period, it experienced three sudden shutdowns. Upon contacting customer service, I was informed it was a hardware issue and was advised to perform a software update via computer. During this process, the representative did not stay on the line, and despite my concerns about potential issues if disconnected, I was assured there would be none. However, the update failed midway, leading me to send the phone for service on October 20. Since then, I've received no updates. A representative scheduled a callback at a time outside of business hours, and now I'm told the process may take an additional 18 business days, with no replacement device provided. I feel let down by Apple's service quality. Every representative I've spoken to has provided incomplete or incorrect information, leaving me to constantly seek updates myself. I urgently need my phone back.