Directv billing me after cancellation

No mistake, this is how the billing as worked for over a year. They no longer prorate final bills. So if your service month starts on the 5th, then you should have canceled 3/4/2020 to avoid paying for the next month. Canceling on the start of the service month means you were correctly billed 3/5 thru 4/4

Here is the notice sent out to all us customers in 2018 about the change:

Please read this if you receive DIRECTV, AT&T U-verse® TV, AT&T Internet, AT&T Phone, and/or AT&T Fixed Wireless service(s). We want to remind you that you’re billed in advance for recurring service(s) and/or programming charges and applicable fees based on the terms of your current service agreement(s) with us. Starting January 14, 2019, subject to applicable laws, we’re updating your agreement(s) to include your recurring service(s)/programming charges and fees won’t be prorated if you cancel the above service(s) on any day other than the last day of your billing cycle. Your service(s) will continue until the end of your billing cycle but you won’t get a refund (prorated credits) for any remaining days left in your billing cycle. For products not listed above, refer to their terms of service for more information.

Questions about this change? Go to att.com/ProrationPolicy for more information and to see the revised section of your service agreement(s).