BONJOUR ACCOUNT... what makes that account different or special

First thing I do is call AT&T and find out what those 12 recievers and 4 WiFi recievers are.

Also is this on a AT&T UVerse account? Is your Cell phone also on AT&T.

It has nothing to do with Bonjour to my knowledge. That is a Network Sharing/connection protocol used by Apple and only Apple devices. Win PCs and Android devices don't use Bonjour (although AI think you can install Bonjour on a Windows PC).

Need to know more about your home setup.

1) AT&T Uverse?

2) AT&T supplied router for Uverse?

3) Cell provider and how many cell phone on your account?

4) What brand of cell phone are you using?

In my honest opinion your AT&T bill should not be $300+ at any time unless you have gone Way Over the DATA limit of your cell account.

Also if you have your phone setup as a WiFi Hotspot Disable that. That is an option in the settings of the phone.

This sounds like a billing error.

When you say AT&T claims you have 12 receivers connected (+ 4 wifi receivers) they would be charging for hardware units (set top boxes, DVRs, wireless TV receivers). They would not be counting how many computers or internet devices are connected to your internet service.

The 12 receivers would have to be connected via wire to your cable installation. The 4 wireless receivers could theoretically connect over the air to your wireless router but that assumes your wireless router has no security enabled and that whoever is using the wireless receivers has enough technical knowledge to hack the AT&T Uverse service; but that is only a very remote possibliity.

I highly recommend that you call AT&T and review your bill and what they are charging for. If you only have 1 DVR/set top box you should only be charged for 1. If there really are more connected to your service, and they are not yours, then someone has hacked into your cable wiring and of course you would want that discovered and terminated. And of course have the charges reversed.