US AT&T SIM Credit - Adding Credit Summary

BACKGROUND
Once you activate the SIM, you will be allocated a number, and your desired plan will go live for 30 days the moment you add enough credit to the number/SIM to cover that plan.

Option 1. 
With a top-up PIN purchased from dataGO [this is emailed to you]
This will let you enter the credit PIN online direct with AT&T when activating the SIM or dial it on arrival 

Before arrival in US
You can now add the credit online as part of the activation process, or log back in later and add it

On arrival in US 
After you have landed, pop in the ATT SIM and dial:  *888*PIN NUMBER# (then press your 'call' button, like making a call)

Option 2. 
Direct with AT&T 
A. Over the phone with AT&T (can do before you leave home)
Call: (+1) 800-901-9878 or 611

OR 
B. Online with AT&T after you have arrived in the States.

OR
C. Purchase a PIN from a retail store in the US and do as above