Polish Telemarketing - why?

I get random calls from time to time and I pick up for the fun of it knowing fully well that it's going to be a telemarketer.

I pick up the call and off they go with their spiel. I repeatedly tell them that I don't speak Polish but they continue sometimes stopping in-between

My question is why do they do this ? What's the purpose?

Even if I say I don't understand Polish they continue and continue.

What's the end goal here?