Lots of pH meters need calibration. In fact, most do. You'll want to follow the manufacturer's instructions with fresh pH buffer solutions (typically a 4.01 and a 7.0), plus a check solution if you have one available.
12.1 sounds very unlikely; if it IS 12.1, you need to call the city sewer&water utility and let them know that they SUCK at their jobs, lol. More likely is that your pH meter is off. It's not a Hanna perchance... ?