Digital life tax problem

I have been a Digital Life customer for years. Suddenly with my April bill, I am being charged tax, where I never have been before. I have spoke to FOUR people at Digital Life and two via chat and nobody can tell me what changed, or will let me talk to anyone in the accounting department.

They keep repeating that tax is determined by the State or City. Well, duh. One person even said that the government goes in and makes changes to the AT&T accounting system(!) and they have no control over it, which seems extremely unlikely. Then they insisted that I call "the government" (who?) and ask them. (So, I'm supposed to call some random person and just ask why my security system bill changed? That'll work.)

Normally if there is a tax change, the Government notifies the business, and the business updates their accounting software accordingly. So the business gets the first notice about the tax change. (I managed an accounting department for 20 years.....)

I have called and spoken to 4 people and keep getting transferred back to the main customer service number. One person even hung up on me(!!!). I have tried chat twice, and was disconnected by a representative once.

How do I know I am being charged a valid tax if nobody can tell me where it came from or what changed? I live in an unincorporated area that frequently is mis-charged tax (when people think we are in the incorporated area). HELP. This is hands down the worst customer service I have ever experienced in my life, and I will be looking to replace Digital Life ASAP as a result of this experience.