Someone called to convince me to switch from landline to digital

She said she was an AT&T price specialist or something and informed me that all landlines will be disconnected soon, so we need to switch to digital. At first the rates she quoted was a lot lower than what we are paying now so I let her explain about the new plan. I asked her to send me an email with exact rates, and the email came from the company called Ring Planet. Is this the company who you work with for your digital phones? The rates she ended up quoting me was actually higher than my current plan rates, and she started sounding fishy, so I told her I would just stick to my current plan. She started threatening then saying our phones will be disconnected and it will eventually be mandatory to switch to digital. If I switch later, I will end up paying so much money. When I said it's okay, she was so (Edited per community guidelines), said okay have a good day and hung up.

Are people from Ring Planet really calling on behalf of AT&T? Why do they claim they're calling from AT&T? She even had our address and account number.

Is it also mandatory to switch to digital? Please advise.

Thanks in advance.