Good to know: To activate a data-only plan, your device must have an AT&T SIM card, Apple SIM card, or an eSIM. If you need a new SIM, order an AT&T SIM card online.
Can’t connect to cellular data
If you got confirmation that your data plan was activated, but you can’t connect to cellular data make sure:
Cellular data is turned on for the device.
Data roaming is turned on if you’re traveling outside the country.