When you're getting calls from different people in close succession, it has to be coordinated - probably by computer. I expect the callers have been instructed not to check your number off unless and until they have a chance to give their spiel, so when you hang up you just go back to the top of the list.

The fact that the calls are so similar is not conclusive in itself - people could be getting a canned script along with their phone list. Put that together with the consecutive-call coordination, however, and it looks very much like a deliberate campaign of harassment. As you note, it's no longer explainable by mere stupidity.

What you have could be a tort lawyer's wet dream, except that the perpetrators have likely covered their assets too well.