said by my thoughts :Authorized Resellers will either be door to door contract sales, or store front that is not company.
I think what the OP is asking is if there are other companies that resell U-verse like DSL Extreme sells DSL over AT&T's lines, but the support is provided by DSL Extreme. The answer to that is no. Uverse support in all cases will be provided by AT&T, regardless of if you buy it direct, from a door to door guy, or a store.