I've been in the telecommunications industry for 13-14 years. I worked for Sprint Nextel for 6 years and...
If it has never been activated, call gophone at 1-800-901-9878 and they can activate it over the phone. If you didn't purchase minutes at a store, you can do it over the phone or online with a debit or credit card.
Option two: take it into a local AT&T store. If you purchased minutes already, take in your receipt/proof of purchase in with you & they can add the time for you as well.
If you are just replacing an old sim card, customer service can swap it out for you.
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AT&T Wireless Helper
Currently employed by ATT Wireless, since 2007.
Hello and welcome!!
To activate your sim card please visit this att.com website..
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call 800-331-0500 and ask for the pre-paid dept. An agent there can either activate the card or determine if you need a new one hence either sending you to your local AT&T store or sending one thru the mail if that is more convienant