Prepaid plan - when does the month start?

When signing up for prepaid service your service does not begin until after you have a SIM card installed and you actually Port your number in and pay for service.

To clarify: If I am not an AT&T Customer currently but want to switch to a new plan online, will my service start the day I check out online, or the day I receive the SIM card in the mail and connect it to my phone? Can I wait a few days after receiving the SIM to activate, and have that day be the first day of the billing cycle? 

Hello @jfar,

Thank you for your inquiry.

Your billing cycle starts the day you pay and activate your service.

You can contact our PREPAID at 800.901.9878 or +1.408.962.1025 (free call from your prepaid phone) for any additional inquiries you may have.

If you ever have any other questions or concerns in the future, feel free to reach back out as we are always here to help!

Jonye, AT&T Community Specialist 

Thanks, but I still am confused. I'm looking at the plan that lets you pay for a year in advance. When I check out, it has me pay right away, but the SIM takes a couple days to come in the mail. So, does it start the day I pay (when I check out online), or does it start the day I plug the SIM into my phone (a few days after paying online)? 

The first payment from the $300 is not taken until you activate the Sim card and begin service.  That is when you begin your 30 day for $25 an eight gig month.  
You have the option of porting in a Number from a previous carrier or taking a brand new number that comes on the Sim.

I suppose I should go into a little more detail on how all prepaid with all carriers work in order to explain the $300 yearly plan.

    The amount you pay upfront as a refill includes taxes and your online account is line an escrow account.  (Money is in an escrow account have not yet been used to pay for a good or service and therefore do not yet transfer to the service or good purchased). 

So here’s how your $300 works:

The $300 is a refill, good for 360 days if you leave it be.  (For gosh sake‘s do not change your plan! )

That $300 plus the tax that you’ve paid is given upfront. The tax you’ll never see again that goes to the fed,  state etc.

The $300 will go into your online account and will sit there for the full year.   Every 30 days it will have $25 deducted from it.
    Of course there will be $25 deducted as soon as you activate service so your balance will show as $275 as soon as you begin service. 30 days later it will be reduced by an additional $25.

Hope that helps explain how it works.

OK, but what if he lets the SIM sit in his mailbox for a couple months before plugging it into his phone?

@jidanni

Until the SIM card is inserted into the phone and activated, set up phone number, alphanumeric password and pin code there is no need to pay it is just a piece of cardboard and Metal. Once the SIM card is inserted and service activated it must be paid for within 26 days or the service is canceled and the SIM card is trash.  Then he would have to start all over again with a new SIM card.