AT&T "unlimited" data plan

I have been an AT&T customer for over 5 years. I have had the unlimited data plan since the first iPhone. At $20 then $30 per month for years I have paid them thousands of dollars for data. AT&T has been throttling my data after I hit 3GB every month. I am on disability and depend on my phone for Internet and keeping myself busy when I can't sleep. They tell me they have to update their network to keep up with demand. How is that possible. AT&T had a monopoly on selling the iphone for years and made a fortune. They should have used that money for updating their inferior network, not paying their executives enormous salaries. Now they have the nerve to try and force people to switch from unlimited data to tiered data plans so they can make more money while trying to blame their users for using a product they offered. If anyone is thinking of using AT&T, think again. Try Sprint for truly unlimited data.