Diane,
I’m not familiar with wifi calls… so I can’t answer to that, but if you’re out of cell signal then assume that you will get no calls and no text (SMS in green) messages.
You will get iMessages (the blue text messages) and can certainly be reached on Facetime, Skype, Whatsapp, etc.
If your Housesitters use iPhones and you have sent/received iMessages in blue with them then you will be fine.
Cheers,
Dave
Wifi calling depends on your provider and your wifi.
I have T-Mobile and wifi calling definitely works on their network, but in my experience the bigger question mark is wifi. Even though I connect to the same three wifi networks at work every day, sometimes I get it and sometime I don’t. My understanding is that for one certain ports need to be open (check), but also a certain bandwidth needs to be detected as available (not always check).
Simon - I have Verizon but have no idea on their internet provider.
Dve - yes, both people have iPhones with iMessages turned on.
Thanks!
Diane
Well if you both have iMessage and you have wifi you should be fine.
I will be spending the weekend in a place with very limited cell phone access (which I am going to love except I want the house sitters to be able to contact me if need be!)
I have an iPad 3 (retina screen) running iOS 8
I have an iPhone SE running the most recent iOS
You can send texts over Messages, iOS routes them over the internet.
FaceTime is an option too. You can also enable WiFi Calling your iPhone in Settings>Phone>Wifi Calling. But if the network is old or weak, it might not work. It has worked in a Starbucks when we were traveling abroad.
Republic Wireless sells Android wifi phones. I have not looked into them in years. You’d have a different number for the trip though.
BTW - I think my iPad is generation 3 (the last 30 pin iPad). It will run iOS 9 which I actually like better than iOS 8. I did not lose any app functionality from the upgrade.
So WiFi settings says I can make wifi calls with my Verizon account. But if there isn’t Verizon coverage that won’t work?
Diane
John - my iPad will go to iOS 9 but iOS 8 makes it so sluggish I was afraid to do the upgrade 
I was forced from 7 when I had the battery replaced.
Diane
No. Actually, you should be able to make calls if you have (good enough) wifi. The idea is that you can use your phone to make calls even in locations where you don’t have Verizon coverage as long as you have wifi.
Simon - thanks! I will give it a shot 
Diane
Wifi Calling will be using whatever wifi network you hook your iPhone in to, not your own Verizon account. It will work if that network can handle it, and many US networks can. If you can’t get it to work in the hotel, it might work somewhere else like Starbucks or Macdonalds. If the hotel does happen to use Verizon as its wifi provider for guests, it the wifi calling would be routed over their account.
I have absolutely no cellular service at my house, and if not for Verizon Wi-Fi calling I wouldn’t have service at all.
Apparently I have to contact Verizon to use wifi on my account?
I know the hotel doesn’t have Verizon service at all.
Diane
Apparently I have to contact Verizon to use wifi on my account?
Nope. You’ll be using the hotel’s wifi account for guests. Just be sure to ask them for the password to log on with when you check in.
I know the hotel doesn’t have Verizon service at all.
It doesn’t matter if they do or not. You’ll be using whatever wifi network it provides. If that wifi network doesn’t work with WiFi calling, other options, like Starbucks, might. There might even be Verizon wifi hotspots you can use. You can check if you qualify here:
https://forums.verizon.com/t5/Fios-Internet/Free-Verizon-WiFi-HotSpots-Now-On-Line/td-p/59445
Diane D wrote: “Apparently I have to contact Verizon to use wifi on my account?”
You have to set it with up with the carrier because in the US they’re required to provide a physical address for 911 use when you’re using wifi, and different carriers probably have different procedures for that. I assume there’s a way to change that address, so you could set it to your motel, then change it back to whatever makes most sense when you come back. But don’t forget to change it when you come back!
Yes, in order to turn on wifi calling, it says to contact Verizon. There is one nearby so I’ll stop in tomorrow. Make sense about 911 - thanks!
Diane
I will be miles and miles from any Starbucks! 
All the major carriers allow WiFi calling, but you must be on a phone that allows for WiFi calling. iPhones since the iPhone 5C allow it. Verizon requires HD Calling which requires an iPhone 6 or later. You also need to set up an e911 address. Most companies allow you to set it up on line.
To turn on WiFi calling, go to Settings->Phone and click on the Enable WiFi Calling switch. You’ll get a dialog box that will verify you’re enabling WiFi calling and have you enter an e911 address. No need to go to Verizon or call them.
If you’ve linked your phone number to FaceTime or iMessages, you can text over WiFi — even to non-Apple devices.
I have an iPhone 6s and just followed your instructions … there is no “Enable WiFi Calling switch” option there.
It’s settings / cellular (at least on my Verizon phone running iOS 11.4.1).