Driving a 44Ω Speaker off a board that expects an 8Ω speaker
Actually the Simcom data sheet for the SIM800H found on that board assumes a 32 ohm element in its output figures, pragmatically speaking your 44 ohms (if that is indeed an accurate figure at audio frequency - doubt has been raised) will probably work, though you could also replace it with a different element, since the earpiece cup readily unscrews.  Given the SIM800H data sheet, if you do go with a replacement you might look at a 32 ohm element, say from unpowered personal audio speakers that plug into a headphone jack.

(If you want to figure out why Adafruit listed an 8-ohm speaker on their product page you could try asking on their own forums - it's entirely possible that was what they had on hand or in stock, they tried it, and it seemed to work)