Smarty is the Best – Full Price Comparison of SIM Only Deals

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I’ve been a loyal customer of giffgaff since I moved to the UK, but as they’ve increased the price recently, I took this occasion to switch to Smarty.

I’ve been using Smarty for about a year now and so far noissues andno complaints about the signal quality. I am satisfied with Smarty because it is cheaper than any other carrier including gifgaff.

It was also easy to transfer my number. I’ve summarised of step by step process on how to do that as well.

If you are looking for a cheap SIM in the UK, Smarty is for you.

What is Smarty?

Smarty is founded in 2017, who only sells SIMs online.
The network is a MVNO (Mobile Virtual Network Operator) operator that uses the Three’snetwork – the signal quality is guaranteed.

It is also ideal for short term stays as you can sign up/renew your plan every month, and you don’t need any bank account or ID to start the contract. It is very convenient to have a SIM even if you have just arrived in the UK.
Not only that, the fee plan itself is unbelievably inexpensive because of the store-less business model.

List of Services


As you would expect from Three, they coverup to 99% of the UK on 3G and 4G.
They also have a group plan (like a family discount) that offers a 10% discount.

I personally found WiFi Calling convenient, as it allows me to make phone calls and send text messages using WiFi, something I had not been able to do with giffgaff.
I often make phone calls indoors, and the signal is sometimes poor in some places. This WiFi Calling is extremely useful in these situations.

Smarty vs other carriers’ plan

The list of carriers available in the UK is below. The cheapest carrier in that capacity band is bolded in red. To ensure a fair comparison, I have used 1 month plans for each carrier. The major carriers Three and O2 are slightly cheaper (e.g. £5-£10 per month) if you sign a long-term contract (e.g. 2 years).

Smarty and giffgaff are MVNO (Mobile Virtual Network Operator) operators that use Three’s and O2’s networds. In addition, Smarty and giffgaff do not have stores and only sell SIMs online which makes them much cheaper than other carriers.

Overseas Roaming
Number of Countries
71 countries71 countries49 countries37 countries156 countries116 countries
EU Roaming
CommentsCheaper than Three or O2
long-term contract plans
Smarty is a better deal
while using the same network as Three
Not much advantageto chooseSmarty is a better deal
due to recent price increases
Number of roaming countriesMany roaming countries, but additional
£2/day is charged even within the EU


Smarty is by far the cheapest. It’s even cheaper than giffgaff.

Here is the step by step process on how to switch to Smarty, with transferring your number

How to switch to Smarty by transferring your number

Although a few steps are required, it is quite straightforward.
It takes one or two days to complete the process, and the phone number is temporarily unavailable during the transfer which only lasts for a few minutes.

How to switch to Smarty by transferring your number
  • Step1
    Insert Smarty’s SIM

    First, you need to purchase a SIM. Smarty requires you to create an account & decide on a plan when you purchase a SIM.
    These are the available plans.


    You can get a £10 Amazon gift card when you proceed from this link (

    You will receive a post like this in a day or two

    イギリス格安 SIM Smarty への移行手順
    Post of Smarty

    A new SIM is inside.

    New SIM
  • Step2
    Activate your new Smarty SIM (do not insert the new SIM yet)

    Download the app from this link ( and login with the account you created when you purchased the SIM.

    イギリス格安 SIM Smarty への移行手順
    App welcome page

    You will then be asked, “Do you want to activate your SIM?”
    Select “Activate SIM”.
    (do not insert the new SIM yet)

    Select “Activate SIM”

    And this time, since we are transferring our phone number from our old carrier select “Transfer my number”

    Select “Transfer my number”

    Then you will see a screen like this.
    Select “Get a PAC code in 60 seconds”.
    PAC (Porting Authorisation Code) is a unique ID that allows you to switch between carriers while keeping your phone number. You will get it in the next step.

    イギリス格安 SIM Smarty への移行手順
    Select “Get a PAC code in 60 seconds”
  • Step3
    Requests PAC (Porting Authorisation Code)

    PAC is very easy to get. Just type “PAC” in a text message to “65075”.
    Like this ↓

    イギリス格安 SIM Smarty への移行手順
    Request PAC in text message

    You will receive the following message from your current carrier. The PAC code is written in the greyed-out area.
    It’s usually 9 digits and looks like this string “ABC123456”

    イギリス格安 SIM Smarty への移行手順
    Get PAC code
  • Step4
    Input the PAC code into the Smarty app

    Return to the Smarty app and enter the PAC code and the current phone number you want to keep on this screen

    Enter the PAC code
  • Step5
    Wait for the old carrier to contact you about account removal

    Then, after one or two business days, you will receive this e-mail from the old carrier
    It says that “the registered payment information has been deleted because the phone number was transferred, but if not, please contact us”.
    It’s OK for us. Let’s move on.

    イギリス格安 SIM Smarty への移行手順
    Account removal email from your old carrier
  • Step6
    Inseret your Smarty SIM

    The final step. Insert your Smarty SIM and launch the app, and you should see a screen like this.
    I bought a 4GB plan, so it says I have 4GB left.

    イギリス格安 SIM Smarty への移行手順
    Transfer complete

How to switch to Smarty by getting a new number

This one is super easy. Once you have the SIM in hand, you can complete it in a matter of minutes.

How to switch to Smarty by getting a new number
  • Step1
    Purchase Smarty’s SIM

    This is the same way to transfer phone numbers.

  • Step2
    Activate Smarty’s SIM (do not insert the SIM yet)

    Similar to the method for transferring phone numbers, download the Smarty application and activate it.

  • Step3
    Insert the Smarty’s SIM

    If you are getting a new phone number, insert the SIM as soon as the activation is finished (takes a few minutes) and you can use the phone right away.

My thoughts

No glitches or complaints. I was expecting slightly a better signal since it uses Three’s network, but I got the impression that there is not much difference between giffgaff (O2’s network).
However, Smarty’s unique feature of being able to use WiFi calls and text messages seems to be very useful.

The price is a small difference from giffgaff, but it is actually cheaper. And yet, no complaints about the signal quality – I’m pretty much satisfied overall.


By comparing the one-month plans of the mobile carriers available in the UK, Smarty was by far the best. No complaints about the signal as well, as it is using Three’s network.

Transferring my phone number was easier than expected, so if you are considering migrating to a low-cost SIM, Smarty is what you need.