DoNotCall List blatantly ignored

Every day, it's the same around 9am and 9pm: When I answer my phone,

it's a hang-up.

When I don't, the somewhat urgent sounding message is

"This is Not a telemaketing call. Please call 866-345-7725. We are

available (days and times)"

There is no identification of the caller or the company.

Please, how can these creeps be stopped?