A Verizon rep told me it's because the taxes are per day, and the total is impacted by different number of days one month to the next. I haven't compared to verify.
when you sign up, it isnt $7 vs $6.93...rather, it is shown as 0 (by not including it.) It doesnt even show up on the cost when you sign up. Suggesting this is a ACT/365 issue is really a slight of hand to ignore the bigger issue.
Also, the calendar can be calculated for the entire year (or the next 100 years for that matter.) It makes no sense that you can sign a 2yr contract and be locked in yet they cant present a table of actual charges for each month for the next 2yrs when you're signing up. Mortgage paymnets also vary by days due to interest accruals, yet they have developed the "sophistication" (read: regulation) to create a chart of what each month's charge will be for the next 30yrs. Not to mention, you could also calculate the yearly regulatory fee and just amortize it on a 30/365 basis if you so desired. There are 10 ways to slice this cake, this isnt rocket science, this is straight up customer abuse and the FTC is just as guilty for ignoring it.
Imagine any other industry that could get away with this. Imagine you sign up for a $13.99/mo Netflix plan and you mysteriously got charged an additional $3 or $5 "because we cant calculate days per month in advance, because reasons."
Or imagine you buy a burger at McDonalds but get charged a different amount once you pay and commit to purchasing the burger "because we cant calculate in advance whether you get 30 fries or 33."