Why is all 3 devices I'm using, well trying to use say this device networked blocked (after I just paid the bill)when I insert my sim card.

Sim card is still associated with the blacklisted device. You have to contact AT&T and correct the IMEI before your sim card can be unsuspended

We have more information that details about the error message, FAQs about the meaning, and how to resolve the error online @Tommy1981probst.

Thank you @formerlyknownas In addition, If you are receiving the error-We're sorry, but this device is blocked from network use. Please contact your wireless service provider. Means the device has been suspended due to being reported lost or stolen or is being blocked to prevents fraudsters from activating and using a stolen device and SIM.

For Prepaid accounts you will need a replacement SIM in order to activate a device other than the device that was blacklisted. Once you have a replacement SIM, and you are the account holder, you can log into your account to restore wireless service. 

1. Go to Account & services > My wireless.
2. Scroll and select the device you want to unsuspend.
3. If prompted, select See device options.
4. Next to the suspended device, select Reactivate.
5. Follow the prompts to reactivate service on your device.

Things To Know:

• Only the account holder can request to remove the device from being blocked. If you are not the account holder or the original owner of the device, AT&T cannot process the request to unblock. We recommend contacting the seller. 
• Request to remove the device from being blocked can only be initiated with the carrier that blocked the device.
• If the suspended AT&T PREPAID device is also blocked, the person whose name is on the bill needs to contact us to remove the block.

We're here if you have any questions. Thank you for contacting AT&T Community Forums. 

Alasani, AT&T Community Specialist