It’s one problem after another for Sprint as it desperately tries to catch up with its rivals in the 4G race while addressing years of issues in most of its key metrics, from churn to debt. In the most recent round of special promotions from the US operators, both T-Mobile and Sprint have been promising aggressive offers, including the latter’s latest ‘half-off’ proposition. This pledges new customers a bill that is 50% of their charges from another MNO, and it has been extended in Q116 to include TMO defectors, as well as those from AT&T and Verizon, and to cover some switching costs such as early termination fees (though subscribers still have to buy or lease a new handset). Despite…