calls for free or discounted service - DirecTV

I was at the AT&T store yesterday. They called directv & I was offered a reduced rare for select customers - $30/month less and free hbo for 6 monnths, that stops automatically - no need to call to cance. Is that a legitimate offer?
Also, I got a call today saying I would get a # of free channels - sorry, she spoke so fast I couldn't even understand her. I told her I do not want any of those free channels & please do not put them on my service. However, I think she told me I could call at the end of the free time - I DO NOT WANT to have to call you to cancel a service I did not ask for in the 1st place. If this continues I will cancel; my service all together. This happened once before & I had to pay for a month of service I did not ask for. What can be done about this?

This question, "calls for free or discounted service," is about DirecTV channels, programming, equipment, and sports.