Is this possible?

[LizzieL]

OK, but I would think most people would be using one of those recent Operating systems, except maybe the people who only have a basic 'phone that only allows them to make calls and text.

It not just a basic text and calls phone that can't use whatsapp. I have two smartphones that take photos, send emails, access the internet and do much more than just basic calls and texts, one is an Android with gingerbread OS and the other is an i-Phone 5. Neither can download Whatsapp App.

Wi-fi calling looks more useful anyway as I can call a landline, but looking at the link cuffie81 provided, I'm not sure I can use it, I have a PAYG i-phone on EE network, and it seems only pay monthly customers can use it.

"EE's Wi-Fi calling service works for pay monthly customers on a wide range of handsets from the likes of Apple, Samsung and LG.
EE also offers the service for pay as you go customers with a Harrier Mini or Microsoft Lumia 550."

[cuffie81]

LizzieL, it looks like EE added support for WiFi Calling on PAYG in June 2021.

The EE Community
EE WiFi Calling: All you need to know
https://community.ee.co.uk/t5/Mobile-Services/EE-WiFi-Calling-All-you-need-to-know/td-p/1057637

WiFi Calling is available to anyone using a compatible phone with an EE pay monthly plan.

From the 9th June we will be rolling this out to all new and existing Pay as you go and Flex customers. You'll receive a text when EE WiFi Calling is available for you to set up.

[cuffie81]

I think you might not be able to use WiFi calling though, given your phones are an iPhone 5 and an Android using Gingerbread. I think they'll be too old.

EDIT: What version of iPhone do you have? Is it the iPhone 5 or one of the slightly newer v5 versions, iPhone 5C or iPhone 5S? Apple added WiFi Calling to the iPhone 5C and iPhone 5S. Whether EE supports WiFi Calling on those models is another question but if you have the C or S version, try enabling WiFi calling and see how you get on.

How to Enable Wi-Fi Calling on Your iPhone
https://www.howtogeek.com/229216/HOW-TO-ENABLE-AND-USE-WI-FI-CALLING-ON-AN-IPHONE/

Make a call with Wi-Fi Calling – Apple Support (UK)
https://support.apple.com/en-gb/HT203032

[LizzieL]

I don't recall a text about wi-fi calling, but it looks like it might be possible after all.
I've just checked my O.S, it came with iOS 9.3, but I am now trying to install 15.5, (taking a long time, and still an hour left) so maybe WhatsApp will work.

Some members on another forum I belong to want to move from an old email based forum (Groups.io) to WhatsApp. 

The phone I actually use for phone calls is an iphone 6 SE, the Android is bigger and the screen is easier to view, so I use it for certain apps, especially Kindle app. Iphone 5 is mainly used for photos.

[LizzieL]

Thanks everyone for your help. In answer to my original question - it is possible!