Some carriers belong to a wireless carrier group. For your reference, we've included these groups below, and also which wireless carriers belong to the groups.
Sprint Group
Boost 534
Boost CDMA 586
Sprint 34
Virgin Mobile 525
T-Mobile
MetroPCS 788
T-Mobile 79
Clearsky
Brightlink 10212
Cellular One of N.E. Arizona 566
East Kentucky Network (Appalachian Wireless) 570
Enflick (Textnow) 10262
Pine Cellular 580
United Wireless 602
Pioneer Cellular 621
Nemont/Sagebrush 796
Leaco 783
Chariton Valley Cellular 701
Bandwidth.com (includes Republic Wireless) 766
MobileNation/SI Wireless 773
MTA Wireless/Matanuska Kenai 774
iWireless 477
Inteliquent 10232
Triangle 10272
Interop
Alaska Communication Systems (ACS)
ASTAC (Arctic Slope Telephone Cooperative Association)
Bluegrass Cellular
Carolina West Wireless
Chat Mobility
Cleartalk (Flat Wireless)
Copper Valley Telecom
Cordova Telephone Cooperative Inc dba Cordova Wireless
Cricket Wireless
Duet Wireless
GCI Communications
Illinois Valley Cellular
Inland Cellular
Limitless Mobile
MTPCS Cellular One (Cellone Nation)
Mid-Rivers Communications
Nex-Tech Communications
Northwest Missouri Cellular
Panhandle Wireless
Pine Belt Wireless
Rural Independent Network Alliance (RINA)
SouthernLINC
SRT Communications
Standing Rock
Thumb Cellular
Union Telephone
Viaero Wireless
West Central Wireless