Douglas Chambers
Analyst · Raymond James
Thanks, LT. Good morning. As LT mentioned, we're off to a good start this year. Let's start with a review of customer results starting on Slide 7. Postpaid handset gross additions increased due to higher switch activity and our ability to capture a larger portion of that switcher group this year versus last year. The switcher group increase was driven primarily by March activity, which was severely depressed last year as a result of the unfolding pandemic and was bolstered this year by stimulus payments.
Our ability to attract switchers increased year-over-year due primarily to the success of our no requirements messaging and lead promotional offerings. We saw connected device gross additions decrease by 3,000 year-over-year. This was driven by lower gross additions of Internet products such as hotspots and routers compared to the prior year where we experienced an increase in demand due to COVID-19. The declines in hotspot and router sales was partially offset by an increase in connected watch gross additions.
Wrapping up this slide, total smartphone connections increased by 13,000 during the quarter and by 56,000 over the course of the past 12 months. That helps to drive more service revenue, given that smartphone ARPU is about $20 higher than feature phone ARPU.
Next, I want to comment on the postpaid churn rate shown on Slide 8. Currently, churn on both handsets and connected devices continues to run at low levels. Postpaid handset churn, depicted by the blue bars, was 0.92%, down from 0.95% a year ago. This was due to lower involuntary churn, which continues to run lower year-over-year as a result of having acquired customers with a better credit mix and improved customer payment behavior. Total postpaid churn combining handsets and connected devices was 1.12% for the first quarter of 2021, also lower than a year ago.
Now let's turn to the financial results on Slide 9. Total operating revenues for the first quarter were $1.023 billion, an increase of $60 million or 6% year-over-year. Retail service revenues increased by $14 million to $685 million. The increase is primarily due to a higher average revenue per user, which I will discuss in a moment as well as an increase in average postpaid subscribers. Inbound roaming revenue was $28 million. That was a decrease of $9 million year-over-year, driven by a decrease in data volume.
One of the factors contributed to this data volume decrease is the merger of Sprint and T-Mobile and the migration of Sprint roaming traffic to T-Mobile's network. Other service revenues were $58 million, an increase of $4 million year-over-year, including a 9% increase in tower rental revenues. Finally, equipment sales revenues increased by $51 million year-over-year due to an increase in units sold and increase in sales of higher-priced units as well as an increase in accessory sales as a result of higher volume.
Now a few more comments about postpaid revenue shown on Slide 10. Average revenue per user or connection was $47.65 for the first quarter, up $0.42 or approximately 1% year-over-year. On a per account basis, average revenue grew by $2.33 or 2% year-over-year. The increases were driven primarily by an increase in regulatory recovery revenues, favorable plan and product offering mix and an increase in device protection revenues.
Turning to Slide 11. As we continue our multiyear network modernization and 5G rollout, control of our towers remains very important. By owning our towers, we ensure we maintain the operational flexibility to add new equipment and make other changes to our cell sites without incurring additional costs, which is very important, particularly given our current technology evolution.
As you can see on this slide, with the assistance of our third-party marketing agreement, we have seen steady growth in tower rental revenues. As I mentioned, first quarter tower rental revenues increased by 9% year-over-year. LT noted earlier the new master lease agreement we signed with DISH Wireless, and we will continue to focus on growing revenues for these strategic assets.
Moving to Slide 12. 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 at the bottom of the slide, adjusted operating income was $258 million, an increase of 12% year-over-year. As I commented earlier, total operating revenues were $1.023 billion, a 6% increase year-over-year.
Total cash expenses were $765 million, increasing $33 million or 5% year-over-year. Total system operations expense increased 3% year-over-year. Excluding roaming expense, system operations expense increased by 2% due to higher certain costs. Roaming expense increased $1 million or 4% year-over-year, resulting from an 80% increase in off-net data volume that was largely offset by a decrease in rates. Cost of equipment sold increased $58 million or 26% year-over-year due to an increase in units sold, an increase in sales of higher-priced smartphones as well as higher accessory sales volume.
Selling, general and administrative expenses decreased $30 million or 9% year-over-year, driven primarily by a decrease in bad debts expense. Bad debts expense decreased $26 million due to lower write-offs driven by fewer nonpaid customers as a result of better credit mix and improved customer payment behavior. We also recorded bad debts expense in the first quarter of 2020 related to the FCC Keep Americans Connected Pledge, which contributed to the year-over-year decrease. In addition, advertising expense decreased year-over-year.
Turning to Slide 13. I'll touch on adjusted EBITDA, which starts with adjusted operating income and incorporates the earnings from our equity method investments along with interest and dividend income. Adjusted EBITDA for the quarter was $302 million, an increase of $21 million or 8% year-over-year. Equity and earnings of unconsolidated entities decreased by $3 million or 7%.
Next, I want to cover our guidance for the full year 2021. For comparison, we're showing our 2020 actual results. Our guidance assumes that COVID-19 does not cause any significant incremental economic consequences that would negatively impact our business. For total service revenues, we have increased our midpoint by $25 million to a range of $3.05 billion to $3.15 billion. This increase is driven by an increase in our projections for build revenues and miscellaneous service revenues.
We have raised the midpoint of our adjusted operating income and adjusted EBITDA range by $25 million by increasing the low end of the ranges with no change to the high end of the ranges, resulting in new ranges of $850 million to $950 million and $1.025 billion to $1.125 billion, respectively. In addition to the increase in our projections for service revenues, the updated ranges incorporate favorability in bad debts and selling and marketing expenses. This favorability is partially offset by an expected increase in loss on equipment for the remainder of the year compared to our earlier projections. For capital expenditures, we are maintaining our guidance range of $775 million to $875 million, and we have provided a breakdown by major category. I will now turn the call over to Vicki Villacrez. Vicki?