This doesn't work for any cellular phone. I used to try that trick with unactivated Nokia 5100-series phones in hopes of making them work in a sort of half arsed prepaid fashion before prepaid became standardized. The calling cards are only for getting cheap long-distance rates, not for making use of an old cellular phone without an active plan. They also only work for landline phones. I haven't seen them even sold since 2012.
Back in the early 1990s, setting the NAM parameters a certain way on an unactivated Nokia and dialing any random number would get you to an automated system called the "American Roaming Network" which would ask you to provide a credit card # and a phone number to dial, which only worked for outgoing not incoming, and I think that went out with AMPS mobile service. It wasn't cheap, either, and cost $4 per minute. Was kinda cool to show off an old bag phone attached in your car to someone though.
The LG125DL is also called the 'LG Classic Flip', a tracfone flip phone that runs either KaiOS or a very stripped down AOSP Android base. The cards they accept are Tracfone prepaid cards, the cheapest being the $10 30 minutes plan. You should be able to find those in any Walmart, Dollar General or Family Dollar among other stores.
Ocnbrz, if you think using calling cards is odd today, heck, I still use a rotary telephone at home.