Mobile data performance very poor since changing phone

[BottlePhone21]

Hi!

About a month ago I got a new phone (Galaxy S24) and put my old physical sim cards in it (old phone was OnePlus 8 Pro).

I have an EE sim and a GiffGaff sim.

So, now the problem:

Since I changed phones, the mobile data performance on the EE sim is very poor, but only in the UK. It shows that it has 4g or 5g connection, but sometimes I can't even send a WhatsApp message and the message takes various seconds to be sent. Opening a simple website is sometimes completely impossible despite the phone showing 5g. 

Scenarios I tried that didn't help:

• Turn off 5g -> no effect
• Swap the sim slots -> still the same, only the EE mobile data performance is poor. GiffGaff sim works in both slots. 
• Roaming in the EU with the EE sim -> Data performance is fine
• Reset the APNs of the EE sim to default -> no effect
• Checked service status for my area -> should be excellent at least on 4g

I'm not really sure what to do anymore. EE data has always been amazing on my OnePlus, but from the moment I changed over to the Samsung phone, it has been worse than poor. 

Any idea what else I could try? 

Thanks

[Leanne_T]

Hi @BottlePhone21 

Thanks for coming to the community. 

Does this happen in more than one area? 

Are you able to try the SIM card in another phone to see if the same happens? 

Leanne 🙂

[BottlePhone21]

Hi! 

Yes, it happens in more than one area (London North, London South, Heathrow Airport). 

If i put the sim back in my old phone, the data connection is working fine again. 

[bristolian]

Depending on your level of technical expertise & interest, there would be ways of potentially identifying the cause of your issues on an Android phone.

A simple approach would be to compare service with other EE users in the same location. Although you mention a GG (O2 MVNO) SIM in the same phone works, testing with another EE user is a better test.

[BottlePhone21]

The EE SIM is a company SIM and nobody else in my office has this issue with their work SIM. 

I'll try out an EE SIM of a colleague in my phone the next days. Maybe that narrows it down 

[bristolian]

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@BottlePhone21 wrote:

The EE SIM is a company SIM and nobody else in my office has this issue with their work SIM. 

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In which case a 2way SIM-swap with a working phone is the ideal next step.

A working SIM in your non-working phone - what result?

Your non-working SIM in a working phone - what result?