Sprint announced Q1 results which showed an improvement in its financial performance and its ongoing network upgrade, but the company’s subscriber performance still raised concerns.

It said that it lost 231,000 lucrative contract customers, “largely due to expected elevated churn levels related to service disruption associated with the company’s ongoing network overhaul”. A loss of 364,000 prepaid customers was primarily attributed to changes that affected its Assurance Wireless arm.

With regard to its recently-announced Framily plans, the company said that it has only been available through its own stores, and has “grown faster than any new Sprint rate plan on record”. So far, nearly three million customers have already signed up, and “additional growth is anticipated as availability expands to other distribution channels”.

The company said that 4G LTE coverage is now available to more than 225 million people, and expects that by the middle of the year this will reach 250 million. The replacement of its 3G and voice network and the nationwide rollout of high-definition voice services are both expected to be “largely complete” by mid-year.

Sprint also launched its Spark service in six more cities, taking the total to 24, supported by 14 devices including the Samsung Galaxy S5 and HTC One (M8). Spark combines the company’s 800MHz, 1.9GHz and 2.5GHz spectrum to deliver higher speeds, and the company is planning to cover “about 100 of America’s largest cities during the next three years”.

The company reported a net loss of $151 million, compared with a loss for $652 million for the predecessor version of Sprint, on revenue of $8.88 billion, essentially flat from $8.79 billion.

Operating income was $420 million, compared with $15 million in the prior year, with the company describing the current period as the “best in over seven years”.

Operating revenue for the Wireless business was $8.25 billion, up from $8.09 billion. It saw an operating income of $490 million, compared with a prior-year profit of $2 million.

Music service Spotify also announced a partnership with Sprint, which will see all customers of the operator provided with a free trial of Spotify Premium.