With one day to go before pre-orders of the Samsung Galaxy S9 and S9+ get underway, AT&T has announced a trade-in deal for the upcoming Android flagships.

AT&T will give customers up to $350 in trade-in credit when they trade in a smartphone and buy the Galaxy S9 or S9+. Here are the devices eligible for trade-in:

• Guaranteed minimum $350 when trading in a Samsung Galaxy S8 family or Note8; Apple iPhone 8, 8 Plus or iPhone X; LG V30; Google Pixel 2/XL Phone
• Guaranteed minimum $300 when trading in a Samsung Galaxy S7 family smartphone
• Guaranteed minimum $200 when trading in any other smartphone with a catalog value of at least $20

In addition to this trade-in offer, AT&T is offering a $150 bill credit to customers when they port a line from another carrier.

AT&T's pricing for the Galaxy S9 is $26.34 per month for 30 months on AT&T Next ($789.99 full retail), while the Galaxy S9+ is $30.50 per month for 30 months ($914.99 full retail). If you take advantage of both of the offers listed above, you'll pay just $289.99 for the GS9 and $414.99 for the GS9+.