AT&T has announced that they will no longer participate in the Plenti rewards program after October 31st, 2017. AT&T was one of the partners that American Express’ Plenti program launched with, recently they added some new grocery partners but otherwise growth of the program has been non existent. Last year the earning rates for AT&T were changed and given the changes T-Mobile & Verizon have made I don’t think AT&T axing Plenti is particularly surprising.
After October 31st it seems that AT&T users will just have access to the AT&T Thanks program. I suspect/hope that AT&T will be making changes to this program to make it more competitive.
Hat tip to @Hsuea001

