Having the exact same issue (iPhone 17 Pro with AirPods Pro 2 and 3). Even swapped out my phone and AirPods and did a fresh iOS reinstall without reinstalling any apps and the issue persisted. Was able to duplicate on other iPhone 17 Pros, Air, and Pro Max across T-Mobile, AT&T, and Verizon. Audio quality for media is perfect, but cellular is impacted. Tried adjusting every possible audio setting to no avail. Transferred same call with lisps (and tinniness) to my iPhone 16 Pro and 14 Pro, and the lisps went away on the other devices. This has been since day 1, out of the box. It is almost as though there is some sort of audio enhancement going on in the background, but it is doing a very poor job. Also persisted on iOS 26, 26.0.1, and 26.0.2. I wish Apple would acknowledge and address this.