Any company that will offer for $10 or $20 an unlimited service, and then bill unknowing customers in the hundreds and thousands ($4,000+) should be shot.
Worked for a major phone company for many years (GTE), slight of hand is their stock in trade. Most folks won’t protest their phone bill, and that is what they survive on.
I scrutinize my phone bill to the max, and protest any true or perceived discretion in my bill. If you protest long enough, your bill will suddenly become true and will remain so.