Don't panic yet. I think the consensus on the Reddit AT&T group is that "bill" is some sort of an estimate which they generate that is always wildly off. That said, I tried AT&T for one month this year because they have the best reception at my house. All of the unadvertised fees (not taxes) were obscene.
Yep. I tried AT&T for 1 month. Got charged Activation fees (which I got them to waive) and all sorts of other fees that weren't fully disclosed when I signed on. For the same service level Unlimited Postpaid x 2 lines + 1 Apple Watch my AT&T bill was >$230/month*. For the same thing from T-Mo it is Exactly $160/month. AT&T was better at my home, but not $70/month better.
*Icing on the cake was I have an employer discount, which they told me AFTER the sale doesn't apply till 3 months in, and is not applied retroactively to the first 3 months. Never again.