AT&T reported adding 541,000 postpaid wireless customers in the final quarter of 2017 as added phones and other devices more than made up for a loss of tablets.

The telecom giant also reported 1.12 percent postpaid churn, a slight decrease from the previous fourth quarter, but touted record-low postpaid phone churn of 0.89 percent.

"We have been on our path for the last four quarters of setting records in wireless service margins and we chose this quarter to reinvest in our customer base," AT&T CEO Randall Stephenson said on a conference call discussing the results. "When you got churn at those sub-90 basis point levels, it seems like the right thing to do."

Both net postpaid additions and churn were ahead of analysts' expectations, and the company reported adding 329,000 postpaid phone subscribers. Forecasters had anticipated AT&T would instead lose some 30,000 postpaid phone customers, according to a note from MoffettNathanson.

The company tallied a net customer increase of 681,000 overall, including 448,000 net smartphone additions. Total wireless subscribers increased by 2.7 million to 141.6 million in the quarter.

Wireless service revenues and adjusted earnings each declined compared to the final quarter of 2016, which the company attributed to "pressure from higher smartphone gross adds and upgrades." Officials also noted that reduced operating costs helped those numbers.

In addition, average revenue per postpaid phone customer decline 2.6 percent year-over-year as users increasingly moved to plans without device subsidies or overages.

Consolidated revenues for the entire company were about level with the totals from the fourth quarter of 2016, but adjusted earnings per share rose in large part due to the effects of tax reform legislation.

AT&T was one of the most vocal proponents of a tax overhaul — amid concerns from critics about its actual economic impact and its potential to increase the national debt — and officials predicted it would bode well for the company going forward.

The telecom's 2018 outlook projected adjusted earnings of about $3.50 per share and some $21 billion in free cash flow.

Officials also noted the potential impact of all states and territories opting into the FirstNet first responder authority, which will allow AT&T to build out a nationwide network in the 700 MHz band with nearly $7 billion in federal reimbursements.

"We ended the year with an exclamation point, thanks to customer growth, tax reform and FirstNet," CFO John Stephens said on the conference call. "And we're very excited about the year ahead."