AT&T CEO John Stankey told managers last year they would need to come back to the core office hubs—18,000 returned.

The tech giant's already unpopular full-week RTO mandate hit another snag when several regional offices said their spaces would not be ready by the Jan. 2 deadline.

AT&T is requiring office employees to work on-site five days a week starting in January, effectively eliminating a recent hybrid option.

AT&T (T) is jumping on the return-to-office bandwagon. The telecom giant is requiring all of its office workers to head back to the office five days a week starting in January, Quartz confirmed. AT&T had formerly implemented a hybrid schedule,