If I remember correctly....(lol, it's been so long since I've had that primitive line), while using dialup online, any phone call would disconnect your online connection.....? Been too long ago to remember.

Don't recall needing a modem for dialup, either. Connection is entirely through the phone line.
Dsl is far better, hands down, and yes, doesn't cost much more than the dinosaur, though that does require a modem.....lol.

Good luck.

Shangrala