Please go to an urgent care or ER now. Sudden hearing damage with persistent ringing (tinnitus) within the first hour is a medical emergency. Early treatment can make a significant difference in recovery.

Also, document everything - screenshot the call log, note the exact time and circumstances. You may need this for Apple support or potential legal action later.

Hope you recover quickly.

I am not a doctor.

If you go to the ER, they may be able to start you on a course of prednisone or similar, which helps lessen damage from acoustic trauma if started within 24 hours.

Have had iPhones since the 5s. On a 17pro now. Never had this happen as an apple software thing, but the new ones (I last had a 14 and didn't have this problem, not sure when the button placement changed) make it easier to accidentally place the user's thumb on the volume buttons (up -or- down) and end up cranking it or silencing it unintentionally.