Unlock IPad

You will need to contact AT&T and ask for the subsidy lock to be removed. Having paid-off the contract, you should not need to wait for end of the original contract - however, AT&T may levy an administration charge/fee to remove the subsidy lock.

Note that if the internal eSIM has been disabled by AT&T (forcing you to use a physical nanoSIM) this is irreversible. While the eSIM may be permanently disabled, you will be able to continue using a physical SIM card with the iPad - subject to removal of the subsidy lock.

iPads purchased through a Cellular Carrier may be subsidy locked - AT&T being one carrier that is known to routinely lock devices to its Cellular network. You may be able to have the subsidy lock removed; where possible, you may be charged. Also be aware that the built-in eSIM of some models of iPad may also have been permanently disabled.

Be aware that Apple cannot (or will not) remove a subsidy lock from a device. Also be wary of third-party “unlocking services” that claim to be able to remove the lock; most are unreliable. A subsidy lock can only be removed by the carrier that applied the lock.

When purchasing a WiFi+Cellular model of iPad, despite seemingly attractive deals offered by Cellular Carriers, purchasing directly from Apple or Apple Authorised Retailer largely removes the risk of encountering a subsidy lock when changing Cellular provider.

The iPad itself isn’t disabled - but if subsidy locked, Cellular connection will only be available for the network to which it is locked.

Devices purchased with a Cellular contract are very often paid-for over the life of the contract - instead of paying “up-front”. So as to ensure that devices are fully paid-for, the Cellular operator will hold-you-hostage - only releasing the subsidy lock when your minimum contractual obligations have been fulfilled (time - or early termination of the contract by “paying-off” outstanding fees).

didn't know they sim locked ipads at all

not sure if apple can do much of the carrier will not comply

you can try contacting apple Support ->  Get Support (apple.com)

You are very welcome.