Verizon is in the early stage of making the shift from 2G and 3G service to LTE and is testing LTE on bands that had been provisioned for PCS, or personal communications service.

Verizon consumers in Cleveland and Manhattan noticed the wireless carrier shut down its 1900 MHz band, which was used to carry 3G service. When the band was reactivated, it was carrying LTE signals.

A Verizon spokesperson confirmed the carrier was testing LTE on the band.

Consumers who have tested the LTE service on the 1900 MHz bands have encountered slow speeds, which illustrates Verizon is only in the early stages of phasing out its 3G network. Verizon had already revealed that it would begin downsizing its 3G network in 2015 to add more girth to its 4G offerings, but it appears the wireless carrier is getting an early start on the process.

Approximately 41 percent of the devices on Verizon's network are said to lack 4G capabilities, so it'll be a good while yet before 2G and 3G are completely phased out.

Verizon' 3G service is expected to be phased out much sooner than 2G. The 2G standard is primarily used for voice and will be remain until Verizon and other carriers make the transition to VoLTE, or Voice over LTE, which offers generally higher-quality voice and is an all-Internet Protocol technology.

The transition to VoLTE will enable Verizon to do away with 2G, but the top wireless carrier will need cooperation from rivals to help the world transition to the standard. For Verizon customers to call AT&T or Sprint subscribers via VoLTE, carriers on both ends of the conversation will need to support the new calling standard.

Back in early November of 2014, AT&T and Verizon revealed they were putting aside their rivalry to work on VoLTE interoperability. The pair hope to roll out VoLTE interoperabilty at some point in 2015.

"Interoperability among all VoLTE providers takes connectivity to the next level with HD-quality voice and additional features that customers want," said Tony Melone, chief technology officer at Verizon. "We're pleased to be working with AT&T as our first interoperating carrier, and we look forward to working with other operators as VoLTE continues to grow."

LTE stands for long-term evolution and is a standard for wireless communication of high-speed data for mobile phones and data terminals. LTE is incompatible with 2G and 3G networks because it has to run on a separate wireless spectrum. The idea behind LTE is to increase the capacity and speed of wireless data networks using digital signal processing technology.