Thanks, LT. Good morning. Let's start with a review of customer results on Slide 11. Postpaid handset gross additions increased by 6,000 year-over-year, largely due to higher switching activity in combination with our strong promotional activity. Of course, this was against backdrop of industry-wide promotional aggressiveness on handsets.
We saw connected device gross additions decline 12,000 year-over-year, driven by lower hotspot sales compared to the prior year when we experienced an increasing demand due to the pandemic.
Next, let's turn to the postpaid churn rate shown on Slide 12. Postpaid handset churn was 1.10%, up from 1.01% a year ago. This was driven primarily by voluntary churn, which continues to run at higher year-over-year -- continues to run at higher year-over-year as a result of increased switching activity and aggressive industry-wide competition. Involuntary churn also increased slightly in the quarter.
Total postpaid churn, combining handsets and connected devices, was 1.35% for the fourth quarter of 2021, higher than a year ago due to the higher handset churn and certain business and government customers disconnecting connected devices that were activated during the peak periods of the pandemic in 2020.
Moving to Slide 13. Prepaid continued to improve compared to the prior year, driven by enhancements to our prepaid offerings throughout the year. We saw prepaid gross additions increase by 7,000 year-over-year and saw an overall increase of 14,000 to a prepaid base compared to prior year-end.
Now let's turn to the financial results on Slide 14. Total operating revenues for the fourth quarter were $1.068 billion, essentially flat year-over-year. Retail service revenues increased by 2% to $696 million, primarily due to a higher average revenue per user, which I will discuss in a moment.
Inbound roaming revenue was $24 million, decreasing 27% year-over-year due to lower data volume and rates. One of the factors contributing to this data volume decrease is the merger of Sprint and T-Mobile and the continuing migration of Sprint roaming traffic to T-Mobile's network. Other service revenues were $62 million, up 3% year-over-year.
Finally, equipment sales revenues decreased by 4% year-over-year, in large part as a result of an increase in promotional activity.
We continue to engage in aggressive promotional activity during the fourth quarter of 2021 to remain competitive with the industry. A portion of the resulting promotional costs reduces equipment sales revenue and increases loss on equipment. In addition, loss on equipment in the fourth quarter of 2020 was mitigated by the impacts of pandemic, specifically lower switching activity and less aggressive promotional activity relative to 2021.
As a result of the combined impact of these factors, loss on equipment increased $24 million year-over-year. This change in loss on equipment however was offset by a reduction in other operating costs as profitability increased slightly compared to the prior year. We expect the aggressive promotional environment, including retention offers to persist throughout 2022 and our guidance for 2022 reflects the corresponding financial impact.
Now a few more comments about postpaid revenue shown on Slide 15. Average revenue per user or connection was $48.62 for the fourth quarter, up 2% year-over-year. On a per account basis, average revenue per -- average revenue also grew 2% year-over-year. The increases were driven primarily by favorable plan and product offering mix and an increase in device protection revenues. These increases were partially offset by an increase in promotional costs.
As you can see on Slide 16, we have seen steady growth in tower rental revenues. Fourth quarter tower rental revenues increased by 9%. We are seeing positive momentum in tower colocation applications, and we'll continue to focus on growing revenues from these strategic assets.
Moving to Slide 17. I want to comment on adjusted operating income before depreciation, amortization, and accretion and gains and losses. To keep things simple, I'll refer to this measure as adjusted operating income.
As shown in the slide, adjusted operating income was $181 million, an increase of 1% year-over-year. As I commented earlier, total operating revenues were $1.068 billion, essentially flat. Total cash expenses were $887 million, a decrease of 1% year-over-year.
Total system operations expense decreased 3%, largely driven by lower roaming expense resulting from lower data rates and lower voice usage combined with lower cell site maintenance.
Cost of equipment sold increased 4% due to an increase in units sold and the higher average cost per unit sold driven by a higher mix of smartphone sales. Selling, general and administrative expenses decreased 4%, driven primarily by decreases in advertising and legal expenses.
Adjusted EBITDA, which incorporates the earnings from our equity method investments along with interest and dividend income was $225 million, an increase of 1% year-over-year.
Now let's turn to Slide 18, where we show our full-year financial results. Total operating revenues were $4.1 billion, a 2% increase year-over-year. This was driven by an increase in retail service revenues due to higher average revenue per user and an increase in equipment sales. Also contributing to the increase were higher tower rental revenues and miscellaneous other service revenues. These increases were partially offset by a decrease in roaming revenues.
Total cash expenses were $3.3 billion, an increase of 3%. This was due primarily to an increase in the cost of equipment sold, partially offset by a decrease in selling, general, and administrative expenses. Excluding cost of equipment sold, cash expenses decreased 1%. Adjusted operating income and adjusted EBITDA, both declined 1% due primarily to an increase in loss on equipment, which increased $70 million from $41 million to $111 million, which is the result of the highly competitive and promotional environment that we experienced throughout 2021.
Next, I want to cover our guidance for the full year 2022. Again, our guidance assumes the aggressive promotional environment that we experienced in 2021 will persist throughout 2022. We expect ranges of approximately $3.1 billion to $3.2 billion in service revenues, $750 million to $900 million in adjusted operating income and $925 million to $1.075 billion in adjusted EBITDA. This guidance reflects our estimates for low single-digit growth in retail service revenue, continued decline of high margin roaming revenue, continued elevated levels of promotional costs, including loss on equipment given the anticipated aggressive promotional environment and modest growth in other cash expenses as we continue to invest in 5G and the growth areas of our business.
For capital expenditures the estimate is in the range of $700 million to $800 million. Our multi-year 5G network modernization program remains on track. We will also continue our targeted millimeter wave buildout in 2022 and begin making investments to deploy the mid-band spectrum we acquired in auctions 107 and 110. We have also provided a breakdown of capital expenditures by major category.
I will now turn the call over to Jim Butman. Jim?