Just noticed you can now use wifi calling and texting on Twigby with compatible phones. Proper wifi calling isn't found on other sprint mvnos like tello, redpocket etc. So gives twigby another extra on the sprint network as well as the verizon roaming.
Definitely another feather in Twigby's cap!
Re: Tello... I am able to make wifi calls via the Tello app (but no texts), even when I'm not on my Tello phone. Just curious... is that different from the wifi calling you are referring to, and if so, how? Inquiring minds want to know... 
The tello app only allows for outgoing calls and texts and not incoming ones. You also have to use the app. Proper Wifi calling is integrated with the main phone dialer and you can set it to come on automatically when you are connected to wifi. Useful if you have a weak cell signal but have wifi. It is more seamless and useful eg if you are overseas you can still receive calls to your us number without roaming charges.
That's a huge difference! No wonder it's a rarity among MVNOs. Thanks for the information.
Be aware that WiFi calling in this integrated manner will use your mobile minutes. WiFi calling via other ways like Google Voice, WhatsApp etc. will not.
Some additions to Twigby's P&T in re to WiFi calling/messaging including some limitations:
[i]WI-FI CALLING AND TEXTING
Twigby may offer voice and messaging services over Wi-Fi (“Wi-Fi Calling”). In order to use this service, an active Twigby account, a compatible phone and SIM card and an acceptable internet connection are required. Twigby Wi-Fi Calling and Texting is available with select phones purchased from our online store. Some phone models previously purchased from Twigby or Bring Your Own Phones may be capable yet cannot be guaranteed. In some cases, different versions of the same phone model may not be compatible while others are. In other instances, the service may not work with phones that are marketed as being compatible. If you do not have access to or lose an internet connection or if the connection is degraded, you may not be able to access Wi-Fi Calling including any 911 service. Not all services are available while using Wi-Fi Calling; for example, services like international calling and texting, emergency alerts, group texting and picture/video messaging are not available.
IMPORTANT – EMERGENCY 911 ADDRESS REQUIRED
To turn on Wi-Fi Calling, you must enter a valid U.S. street address where you want emergency services to be sent if you call 911 from your phone. This location information is required to comply with federal 9-1-1 regulation within the United States. If you are not prompted for your address when turning Wi-Fi Calling on, you remain responsible for manually adding and updating the address within the Wi-Fi Calling menu of the phone. It is also very important that you update your address whenever your location changes, because this is the location that will be given to emergency service when you dial 911. You can change your emergency 911 address by going into the Settings menu on your device.
WARNING ABOUT 911 CALLS OVER WI-FI
When calling 911, always tell the operator the physical address of where you are. Your 911 call will go over Wi-Fi only if the cellular network is unavailable. 911 calls made over Wi-Fi may be delayed or unsuccessful; for example, if the 911 system doesn’t recognize the address, electrical power is out, or your Wi-Fi connection isn’t working. Emergency services will be sent to the address you provided on your device, so please update it as you change locations.
WI-FI CALLING – IMPORTANT BILLING INFORMATION
Any Wi-Fi call made to a U.S. number will be treated as a domestic call, no matter where the call originates. Any Wi-Fi call made to a non-U.S. number will be treated as an international call. Please refer to your service plan for more information on the use of the Wi-Fi Calling[/i]