No pro rata of charges

Please consider your billing cycle when deciding to transfer your service to another cellular provider. 

Excellent advice.

I don't suppose you read the terms of service when you signed up for T-Mobile? They don't prorate either. Nobody does.

This is industry-wide standard for all cellular, and as far as I know internet and TV providers as well.

https://clark.com/technology/switch-cell-phone-need-to-know/

Guess what the first item on the list is... Yup

I do not expect a refund or any type of sentiment.  I do not expect AT&T to change a policy based on the expectations of one user.  I will say that AT&T has lost me as a long time loyal customer, not just now, but in the future as well. 

The opportunity cost of $123.11 is, for AT&T, my loudest voice telling everyone who will listen why I am not a customer. 

🤣

Be sure you warn T-Mobile they're at risk of incurring equal wrath if they hold you to their policy like att did.

I paid full price for a month of service and received a partial day.  You may think that is fair, but I am not a fan of paying for things I don't receive.  

Do you complain to the waitstaff if your guacamole is missing?

Irrelevant.  

These services are not prorated.  When we sign up, we agree to it.  As the article suggests, know how it works and plan ahead.  

I am honestly not sure if this policy was in the agreement when I signed up with AT&T 15 years ago.  I do know the possibility that AT&T would charge me for a service I did not receive did not enter into my thinking when I was planning the move to T-Mobile.  If it had, I would have gone to Costco on Friday night instead of Saturday morning.

I had planned to move phone and internet back to AT&T when they finally got fiber rolled to my neighborhood.  Working from home, I needed a faster connection than uVerse could provide.

Now that AT&T decided that keeping my $123.11 was more important to them than my returning as a customer, I will exhaust all other options before signing up with them again.

Saying you're lost as a customer (now and in the future) because they don't prorate the bill doesn't mean much. This is pretty much standard in the service industry (TV, phone, etc.). You might as well be saying you will not have any phone ever again because they don't prorate.

Yes this change happened years ago. I am not a fan of it. I agree be aware of billing policy before canceling, whether you read it from the Terms of Service (ToS) or discuss with the agent over the phone before you finalize closing the account (though I recommend ALWAYS read as agents are still human so can make mistakes).

Do you complain to the waitstaff if your guacamole is missing?

Do you expect to pay LESS if you don’t eat all the quacamole?

You order quacamole.  They bring the quacamole.  You eat half the quacamole.  You still pay for the quacamole.  They do not pro-rate the quacamole.