Sprint and T-Mobile hope to join forces next year, but for now they are still competitors. On Thursday, Sprint followed through on a previously reported plan to offer discounted service to customers age 55 and above. The plan offers unlimited data, talk and text and encourages customers to purchase two lines; the first is $50 per month and the second is $20 per month. (Customers age 55 and over also have the option of purchasing just one line for $50 per month.)

The plan is very similar to T-Mobile's Unlimted One 55+ plan, which the carrier launched last year. T-Mobile said its plan was aimed squarely at customers of AT&T and Verizon, and Verizon countered with a similar plan of its own in Florida earlier this year.

T-Mobile's plan for seniors may have also brought some Sprint customers over to its network, but now those customers will be able to get almost the exact same deal without switching carriers.

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Like T-Mobile's plan, Sprint's Unlimited 55+ plan includes unlimited data for devices used as mobile hotspots, but that data will be delivered "at 3G speeds," Sprint said. In addition, Sprint is offering free global roaming to more than 185 countries. T-Mobile's plan offers free roaming in Canada and Mexico.

Sprint is also promising customers "DVD quality with speeds up to 480p+ resolution, music at up to 500 kilobits per second, and streaming cloud gaming at up to 2 megabits per second." The company said its national average download speed is up 35% from last year, thanks to its increased investment in network technologies like massive MIMO.

Sprint said that its network investment will continue per plan this year while it waits to find out whether regulators will approve its plan to merge with T-Mobile. Sprint is upgrading its cell sites nationwide to support all of its spectrum bands: 800 MHz, 1.9 GHz and 2.5 GHz. In addition, the carrier is adding new small cells and macro sites, and preparing to launch a mobile 5G network next year.

At an investor conference, Wednesday, Sprint's new CEO Michel Combes said the carrier will spend between $5 billion and $6 billion in 2018 in order to be ready for 5G.

Combes said Sprint's goal is "parity" in 4G and "leadership" in 5G. He added that most of this year's network investment will be for 5G-ready technologies that can be used whether Sprint merges with T-Mobile or continues as a standalone company.