Why wasn't my account deactivated?

That is definitely a postpaid bill. It probably doesn’t have any new plan charges on it meaning your account has been closed and that is a final bill. If you never intend to open an ATT account again, you can just ignore it. ATT will turn the bill over to a collection agency and put a hit on your credit report, though I have no idea if that will effect you in the UK. You definitely did not have a prepaid plan. You actually needed to call to cancel.

The only way you would owe is if you had signed up for postpaid. Prepaid doesn’t have a bill and doesn’t accumulate a balance owed. You are correct prepaid cancels once you stop paying

Thank you for helping me, but I have a bill right in front of me with 400 dollars due on it, I know for 100% certain that I did not set up a contract and that my sim was prepaid and I paid it manually every month, I did not setup an auto pay. Could this bill be an error, if I just ignore it will I be ok? I don’t even have the SIM card anymore it’s been destroyed. 

No one here can see your account or bill to answer. Again, prepaid does not have a bill. It’s either a mistake or you didn’t have prepaid. What exactly is the bill for? $400 is very high for a final bill for a single line unless it is for several months worth of service, which it would be if you just stopped paying. The bill would have the name of the plan on it. What plan did you have? 

I stopped paying for the service in March so this must be several months. The bill doesn’t have the name of a plan on it? Here’s a photo. It gives me my account number but that’s it. I’m pretty sure I can just ignore it? But I would like to know why my account has not been deactivated?

We need to see the service summary of account charges that should be on page 2.

This is all it says. There’s nothing about the plan sadly. 

There has to be more charges listed somewhere. That is only $6.41.

Nope that’s both pages, there’s 397 dollars from my last bill apparently even though I stopped paying and it was a prepaid account. I should not be receiving bills, thank you for helping me out.  

But I had to pay every month and when I didn’t pay my 4g would stop working until I paid again. I don’t ever intend to open an ATT account again. However this was very unfair on me since I had very little information given to me.