Frontier is a scam, they won't let me cancel and keep sending me fraudulent bills

TL;DR: Frontier won't let me cancel without a PIN they never sent, keeps billing me, and is adding fake fees. What are my options?

Hey Reddit, I'm stuck in a Kafkaesque nightmare with Frontier Internet and could use some advice:

  1. Got Frontier, but service kept dropping.
  2. Tried to cancel, but they demand a PIN (Is this even legal?).
  3. Requested PIN, never received it (months have passed).
  4. Keep getting notices about unpaid bills and service cancellation.
  5. I tell them to cancel, but they ignore me and add bogus fees instead.
  6. Suspect they're inflating the bill to sell to collections.

I'm at my wit's end here. What should I do? Do I need to lawyer up? Has anyone successfully escaped Frontier's clutches?

Any advice, similar experiences, or legal insights would be greatly appreciated!

Edit: I'm located in CA, if that helps with legal advice.