Which UK networks are supported for roaming?

[NFH]

I have always found that I can roam in the UK only on 3 UK and O2 UK, and not on Vodafone UK or EE.

I recently had a technical issue when roaming on O2 UK, and Three customer services asked me what happened if I manually selected Vodafone UK or EE. I replied that I have never been able to roam on these two networks, as my iPhone always displays "No Service" when I manually select them. He responded that Three Ireland has four roaming partners in the UK, including Vodafone UK and EE.

Is this true? Should I be able to roam also on Vodafone UK and EE? If so, why have I never been able to do so?

[NFH]

Last weekend, my girlfriend and I could both roam on EE UK and Vodafone UK. I discovered it because I was waiting somewhere where there is bad 3 UK and O2 UK coverage, so my iPhone automatically switched to EE. But neither of us can roam on EE UK and Vodafone UK any more, even if we manually select the network. Can anyone confirm what is causing this, given that Three Ireland say that customers should be able to roam on all four UK networks?

[Three_Niall]

Hey @NFH, I'm happy to clear this up for you here, when you are roaming there isn't a guarantee that you will be able to connect to specific networks. When you are abroad we recommend having the phone set to automatic and your phone will be redirected to the best available network in the area that you are in.

[NFH]

Hi @Three_Niall. Thanks for your reply. I should clarify that we are manually selecting a network only for diagnostic and testing purposes. Most of the time we leave our iPhones on automatic network selection.

Three Ireland says that it supports roaming on all four UK networks, which are:

• Three UK
• O2 UK
• Vodafone UK
• EE

I have never been able to roam on Vodafone UK or EE in the many years that I have been a Three Ireland customer. My girlfriend can't do so either. We both see "No Service" if we manually force our iPhones to roam on these two networks in strong coverage areas. The exception was last weekend when we could both roam on Vodafone UK and EE.

Despite having roaming agreements with all four UK networks, does Three Ireland deliberately turn off the ability to roam on Vodafone UK and EE because it pays lower wholesale prices to Three UK and O2 UK, the latter probably being a legacy of O2 Ireland's relationship with O2 UK? If not, what is the explanation for Three Ireland customers being unable to roam on Vodafone UK and EE?

[Three_Niall]

The reason that we recommend to have your mobile data network selection set to automatic is because your phone will automatically be redirected to the best network where you are.

For example if you are on automatic and you have connected to Three UK and then you try to manually select other networks and there may be no service like you are describing. We can't guarantee that all networks are always going to be available as while it may be possible to connect to other networks we wouldn't have any control around these networks however in the situation that you are unable to connect to any network we would be able to have our team investigate this further. 

[NFH]

Thanks @Three_Niall. I accept that Three can't guarantee anything, but what could cause a long-term inability by all Three Ireland customers to roam on two specific UK networks with strong 3G, 4G and 5G overage?

[Three_Niall]

As receive coverage through a radio-based signal, several factors can dictate the coverage or the networks that you can connect to, especially while you are abroad. While I understand that you are specifically looking at Vodafone UK and EE, the only way you could guarantee that you are going to connect to a network is by unlocking your phone and using a SIM from that network while you are in the country but if you are in the UK and you are connected to Three UK, this is an award-winning network so you would be able to receive a strong signal from this network.

[NFH]

Three UK's network is heavily congested. I know because I am also a direct customer of Three UK for voice calls on my UK number. As a consequence of Three UK's congestion, I get much faster data speeds when roaming on O2 UK than on Three UK.

How do you explain the following symptoms, which have been consistent for many years?

• Using an EE eSIM, I get maximum 3G, 4G and 5G signal strengh on my iPhone 15 Pro, yet when I try to connect to EE in the same place using my Three Ireland esIM, my iPhone shows "No Service".
• Using a Vodafone UK nano-SIM, I get maximum 3G, 4G and 5G signal strength on my iPhone 15 Pro, yet when I try to connect to Vodafone UK in the same place using my Three Ireland esIM, my iPhone shows "No Service".

I am not looking for guarantees, only a plausible explanation for the blocking of roaming on EE and Vodafone UK.

[Three_Niall]

There isn't a block on roaming with EE and Vodafone UK and if they appear in the list of available networks then they would be available to attempt to connect with these networks however I would be unaware if there are additional steps you would need for connecting with these networks for example updating the APN settings to matching these networks. 

The reason why you would be able to connect to these networks perfectly while you are using the SIM's provided by these networks is because you are using their SIM cards and their network settings would automatically set up on the SIM cards however when you are roaming the reason we recommend leaving the network selection on automatic rather than manual is because the device will automatically connect to the best available network using the settings on your device without the need for you to troubleshoot within the settings to receive a connection.

[NFH]

APN settings are specific to data. They make no difference to the ability to roam on a network for voice and SMS. If the APN settings are wrong, you can still connect to the network but can't use data. So APN settings have no bearing on this.

I know why I can connect using the two UK networks' own SIMs. The question is why roaming consistently doesn't work on these two UK networks using a Three Ireland eSIM or SIM, despite excellent coverage and strong signal strength.