If you’re trying to use it for Caller ID, most generic “56K V9.2/V9.0” modems work provided you choose “Generic Modem” for Devices in SambaPOS.
I’m personally using this modem:
https://www.amazon.com/gp/product/B077YBTC2J/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1#customerReviews