Data usage has gone WAY up

data is not reported real time it can be data used during the day or previous days 

forgot to say - this is pertaining to my iPhone!

What does your phone say it has used data for?

https://support.apple.com/en-us/HT201299

We want to help you manage your data usage, VolDiver.

Tracking your data use is your first line of defense. Here are some simple ways to stay informed:

• Use myAT&T to review your current balance info for talk, text, and data use. If you have linked accounts, select My wireless and See all my usage.
• Dial star services from your AT&T wireless phone just like you're making a call. We'll text the info to you. To get data and text balances:

• 1. English: *3282# (*DATA#) 
  2. Spanish: *3286# (*DATO#) 

Here are some activities that tend to use a lot of data:

• High-definition video streaming (900MB per hour).
• Video conferencing, like FaceTime and Skype (480MB per hour).
• Standard-definition video streaming (240MB per hour).
• Online interactive gaming (60MB per hour).
• Music streaming (30MB per hour).
• Downloading and viewing movies or other large data files.

Wondering how you can take control of your data usage? Look no further:  

• Use Wi-Fi whenever its available. 
• Use Stream Saver. 
• Use the built-in data monitoring feature on your device. 
• Temporarily disable data on your device. 
• Try switching to a plan that better fits your needs.

******If your plan does not include unlimited talk, your voice usage is rounded up to the nearest minute and if you exceed your plan voice allotment and any available Rollover Minutes, we will calculate Anytime Minute overages. You will be billed at your overage charge per minute for these overage minutes. If your plan does not include unlimited text, you will be charged for each message that exceeds your messaging allotment. Charges apply for each text/picture/video message sent and received that exceeds your plan's limit. If you don't have a messaging plan, pay-per-use rates apply. 

You can use your Customer Service Summary (CSS) to get a breakdown of the charges.

As @Constructive mentioned, time stamps for current data or text usage may be off by up to 4 hours in myAT&T. Here are some things to keep in mind:

• We usually update recent data use every three hours.
• You may not be able to see usage since your last bill online if you have a new account or changed your plan in the middle of a bill period.
• Usage info may not be available while we’re processing your bill. Usage generated near the end of a bill period may not show up until the next bill period.
• Additional delays of up to 60 days are possible if the usage takes place outside the U.S.
• For wireless roaming use, which is based on call records from other carriers, delays are normally 2-10 days but could be more than 60 days. Some use may display online but be billed during a later bill period.
• For talk use, you may see airtime for voicemails and other calls that aren't billed. If you use more minutes than are included in your plan, we'll deduct the minutes from your available Rollover Minutes. After that, we’ll apply a per-minute charge.

Thanks for visiting our Community Forums! We hope this information helps. 

Sydne, AT&T Community Specialist

Thanks!  After 2 chats and over an hour working on this, AT&T said it was a "technical glitch" on their end and they are restoring my data.  We'll see...

Icloud backup(iphone)?

background app updates?

auto ios update turned on(iphone)?

icloud photos/video enabled?

no wifi apparently.  So turn off all these and disallow cellular data for certain, or all your apps. 
maybe youve become a cryptomining bot?

or some other bot? Better check your app usage. Battery will show some. The App Privacy Report will show more. But this is all iphone.

Technical glitch? Only you? Or is this a class-action (Edited per community guidelines)?

@Oldo read your terms of service your limited to binding arbitration

@Oldo

AT&T is not responsible for your phone using excess data. 

A courtesy credit and claiming it was a system glitch when it probably was not, does not mean At&t did anything wrong or unusual.  

460801kb is less than half a gig of data. Something that can easily be consumed if you spend a little time watching YouTube videos or streaming music is high quality. 

One person with a problem does not make a big suit.  And SCOTUS prohibits individuals from filing such against your provider.    You are limited to small claims or arbitration to resolve an individual problem which would take months and months. Or you could be like the original poster and call and get your answer or resolution or at least a compromise the same day.

BTW, with a cost of prepaid unlimited plans coming down to as low as $30 a month, if you are still using a metered plan you are only hurting yourself, and denying yourself the lack of anxiety that goes with cheap unlimited