Unable to Login
I reside in the UK but I purchased in March 2018 a prepaid AT&T sim which I use when I am in the USA. I've had no problems accessing MyAT&T and the last time I used the sim was in May 2019. I will be in the USA next month so was looking to check my balance and top up as required but cannot access my account. I've tried to use the phone by dialling (*777) and now receive a message saying "Not registered on network". I know I use the sim card infrequently but I have not received any contact from AT&T to advise me that my number would be disconnected so I am looking for some assistance to allow me to check my account balance and keep topped up.