I was talking about wireless companies in the USA. You stated Sprint is using SERO to compete with Helio. It's the other way around. SERO has been offered LONGER than Helio (USA) as a MVNO carrier of Sprint. As far as Helio standing it's grounds, GREAT. The grounds that Helio walks on is Sprint, and Sprint greatly appreciates Helio choosing Sprint as THEIR network.
Sprint has a reputation of offering TOO MANY options for their customers. That is why Sprint gets a bad wrap. More options, more problems.

P.S. Sprint has been around longer than SK Telecom. Just a little FYI. Sprint est.1899 and SK Telecom est.1984

-Yean