AT&T made a major move into the prepaid space yesterday when it announced it would begin selling the Android-based LG Thrive to its GoPhone customers.

The Thrive will be AT&T’s first prepaid smartphone. The introduction of the device could mark a major strategic shift for the operator, which historically has mostly shunned lower-profit prepaid services in favor of postpaid customers.

“Thrive brings more choice and more value to our GoPhone customers by delivering the benefits of a smartphone, balanced with functionality and affordability,” AT&T prepaid executive Judy Cavalieri said in a statement.

AT&T also cut the price of its prepaid data plans. Its $5 prepaid data plan now offers 10 MB of data instead of 1 MB and the cost of its $20 plan for 100MB has been dropped to $15. The operator also began offering a new 500MB prepaid plan that costs $25.

The move comes just weeks after AT&T announced its plan to acquire T-Mobile USA.

AT&T could use its beefed up prepaid offerings to court T-Mobile’s base of lower-ARPU customers, who may not be attracted to AT&T’s higher priced service plans. A sizable portion of T-Mobile’s customer base is comprised of prepaid customers.

The Thrive will launch on April 17 in retail stores along with a postpaid version of the same device, the LG Phoenix.

Both devices come equipped with Android 2.2, a 3.2-inch touchscreen and a 3.2-megapixel camera. The Thrive will be offered in silver for $179.99 and customers must purchase a GoPhone smartphone plan. The Phoenix will be available in dark blue for $49.99 and requires a two-year contract.