Sky Mobile is running a surprise sale, cutting prices on a number of device tariffs, with some of the best deals on its . It joins O2 and Vodafone, who also have sales right now, making it a great time to consider a new SIM.

If you're a high data user then Sky Mobile’s unlimited data plan might appeal, especially as it beats O2 and Vodafone on price in the latest sale. Discounted by £9 a month, you can get unlimited data for .

It normally costs £29 a month, so you'll save £108 in the first year of the 24-month contract. That's cheaper than O2’s equivalent which is £22 a month and Vodafone which is £24 a month.

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Sky doesn't have a cap on the amount of data you can use, so there’s no "fair use" policy here, so you can use as much as you want. With great 5G coverage – powered in this case by O2’s network – it’s a great choice for those who want to use a lot of data.

It also includes roaming across Europe (but check the supported countries before you travel) while you also get unlimited calls and texts.

While Sky Mobile is known for offering great value for money, there are some advantages to choosing another network. Normally, I'd recommend checking your connectivity before choosing, but if Sky Mobile doesn't work, then O2 won't work either, because they run on the same network.

In that case, Vodafone might be a better option. The Unlimited Plus offering is a little more expensive (it'll cost you £48 more in the first year) and it comes with a 100Mbps top speed. Vodafone Unlimited Plus is also discounted, now .

That’s still a saving of £108 across the first year.

There's also a sale at O2 and there's a discount on unlimited data here too. The O2 Unlimited plan is in an online only deal. This tariff doesn’t come with all the Extras that some of the more costly tariffs do, but you're still getting that unlimited data at a great price.

These summer sales aren't running for much longer, with O2's sale finishing on 4 June, and Sky Mobile coming to the end of its Week of Treats. It's worth remembering that these are SIM-only deals and you'll have to buy the phone separately.

That comes with an advantage, because you can change your phone as often as you like and it gives you the freedom to shop around for the best deals, to buy refurbished devices or to get the latest phones as soon as they launch.