It's safe to say T-Mobile's latest efforts aimed at migrating Sprint customers and integrating the "Now Network's" mid-band spectrum to improve capacity and boost speeds didn't go particularly well, but it actually pays off to stick with the soon-to-be-retired carrier a little longer.
That's because existing Sprint subscribers can now add a line of unlimited service to their accounts at absolutely no charge without doing... much of anything (via Slickdeals). All you need is a wireless account opened prior to June 17 with at least one active voice line on it.
If you can meet these two very simple requirements, there are three options to actually join Sprint's sweet "Unlimited Line on Us" promotion, although first and foremost, you'll want to log into your account to make sure you qualify for this excellent freebie.
After doing that, you're free to "bring your own phone", i.e. add the gratis new line to a device you already own, as well as buy a new phone to activate the free line on or even reserve your free line now and add a phone later. Talk about incredible flexibility, not to mention incredible affordability, with your free line including unlimited talk, text, and data, with a 480p video streaming cap, and presumably, no mobile hotspot allotment.
That amounts to a colossal savings of more than $400 a year, mind you, and yes, you can keep your $0 line forever as long as you maintain your account in good standing. That means you'll be allowed to switch your account to T-Mobile when the time comes without having to pay anything extra or give up any current voice lines.
Basically, that makes this an even better deal than Magenta's own free third line promo since you're going to end up using the "New T-Mobile" network anyway and you can score your very cool gift even if you only have one active line of service to begin with. In case you're wondering, Sprint doesn't list an expiration date for its latest special offer for existing customers, but we're fairly certain something as great as this can't go on forever.