Based on the address, the stations named "Unterer Graben 25" on eCarUp are probably in the Parkhaus Central.
Their website says they have 4 charging stations, but no details about the operator, payment method or tariff https://parkhaus-central.ch/parking/
The parking also has a page on the Indigo website as they seem to be the operators. But unlike their parkings in Lausanne, they don't seem to operate their own chargers here https://ch.parkindigo.com/de/parkings/parkhaus-central/ eCarUp indicates the operator name as St.Galler Stadtwerke.
The information on the website indicates the parking was (re)opened on March 20, 2025. In the live data, the chargers were visible from March 19, so they must have been available from day one.
Despite showing 40+ pictures of the brand new parking on their website, there isn't a single picture where I can see the chargers. On one of the pictures of level -1, we see the edges of 2 green parking spots with EV signs, but the wall and chargers aren't in the shot. The 2 other charging spots are either not painted green, on a different level, or against the wall from which the picture is taken.