WiFi calling on sim only

[BevG]

If I get an o2 sim only contract (providing my own phone) will I be able to use WiFi calling?

I was on a pay monthly tariff but I’m having problems with my current phone. I really don’t want to sign up for a new 3 year contract. I didn’t realize when I signed up that it was for 3 years. 
so I am going to purchase a new iphone from Amazon directly (not a third party), will I be able to use WiFi calling?  Tia

[MI5 · Accepted solution]

@BevG 

You can as long as you buy a compatible phone 

https://www.o2.co.uk/connectivity/wifi-and-4g-calling

[Rob521]

I have just been told by O2 that I can not set up WiFi calling on my phone, originally bought from Carphone Wharehouse but with an O2 sim only contract, because it does not have O2 firmware as I did not originally purchase it from O2. 

[Enlli]

@Rob521 What phone? O2 haven't had firmware specific to them for some time.

Just ring back and ask them to turn WiFi Calling on. Nothing to do with them what phone you use, probably pushing for a sale.

[Bambino]

@Rob521 O2 and Carphone Warehouse cut ties several years ago. Your phone may be too old and not be capable of WiFi calling.

Carphone Warehouses loses O2 aft... - News - Mobile News (mobilenewscwp.co.uk)