Sprint will begin charging Nextel iDEN customers who do not upgrade to Sprint's CDMA push-to-talk service an extra $10 a month starting in January.

The move is apparently designed to encourage customers migrate from the iDEN network, which Sprint plans to shut down on June 30, 2013. The charge will not apply to CDMA customers.

"Customers that migrate prior to January will likely find a price plan comparable to what they have now," Sprint spokesman Mark Bonavia said in a statement. "They are also eligible to receive a variety of very attractive device offers."

Sprint, which acquired Nextel in 2004 for $35 billion, announced nearly two years ago that it would phase out Nextel's iDEN technology starting in 2013. The phasing out of iDEN is part of Sprint's larger Network Vision plan, which is an overhaul of its existing network and move to 4G LTE technology.

Despite offering a 2G technology largely useful for talk and text messaging, iDEN continues to have a loyal following among those in the construction, public safety, and enterprise areas. However, Sprint recently decided to stop offering iDEN products.

Instead, Sprint has been pushing customers to Sprint Direct Connect handsets, which offer the same kind of push-to-talk capability of an iDEN phone. Sprint has previously attempted to make this push, but the technology wasn't ready.

[Via Phone Scoop]