For those who bought through Apple, call customer service, explain the issue, have them refer to a Google search to see how widespread this is, and ask for your money back. Luckily my iPhone 11 Pro didn’t sell, moved the SIM to that phone and skipping the 12 altogether. I rely on my phone too much for work and can’t afford these issues. I purchased on launch day, and past the return date, they still did a refund.
For those who purchased through your carrier, request they swap to an 11, carriers can be flexible depending on the rep. If you don’t hear what you want from the first, call back and try the next.
In all cases, be polite!!