will now sell you a mobile phone contract, meaning you can buy not only the hardware, but the tariff to go with it.

Amazon has been selling smartphones for a long time, offering devices like the Moto G as a retail partner for Motorola before Moto opened its own UK store, in many cases Amazon offers good SIM free prices. Now there's the option to take an O2 contract with many of the top phones it offers.

When you search for a handset on Amazon, you'll now be presented with the option to buy SIM free or to take a contract. You can upgrade, or take out a new contract, with the option to add Bolt Ons and so on.

Once you've found the phone you're interested in, you can then pick from a wide range of O2 tariffs, with Amazon breaking down the costs, and showing you the cheapest monthly cost as the best deal.

You can opt to pay some upfront costs, to reduce your monthly bill and Amazon also gives you the approximate total cost of your contract, but notes that on these 2-year contracts, the prices will be adjusted in line with the retail price index from 2015.

Surprise surprise, there's no option to buy the iPhone, probably because of the volume of iPhones that O2 sells, they want to keep it all in house. We also noticed that there's no Moto X.

We asked Amazon why there was no iPhone and received the following response: "We are currently offering more than 90 phones including a great selection of smartphones, such as Fire phone, and will continuously work to improve and expand selection."

You can get many leading smartphone handsets however, including the HTC One M8, Sony Xperia Z3, Samsung Galaxy Note 4, Nokia 930, LG G3, and the BlackBerry Passport.

Of course, you can also buy the Amazon Fire phone. 

If you're looking for an HTC One M8, then Amazon is offering it on a 2-year O2 contract with 1GB data and unlimited text and calls, for £28 a month.

We found the same deal is also available through Carphone Warehouse, so there's no difference where you buy, although note that this is an online deal, you can't get it in stores.

Sony's Xperia Z3 is a great handset. Amazon offers it free with 2GB data and unlimited text and calls for £38 month. That's the same price as O2 themselves. 

However offer the same phone with 5GB of monthly data for £38 a month. There's also £76 cashback offered on this deal.  

The LG G3 is aggressively priced. You can get it for £28 a month with 1GB data and unlimited calls and texts.

That's a pretty good price and it's the same as you'll find through other retailers. However, should you plump for it at Carphone Warehouse, you'll get a free Quick Circle Case.

One of the latest phones, the Nokia Lumia 735 is available for £15 a month. You only get 300MB of data, but you get unlimited text and 300 mins of calls. 

That's the same deal as you'll find elsewhere.

Finally, lets look at the Fire phone. If you want Amazon's own phone then buying through Amazon with a contract looks like the best deal.

Amazon are offering a 1GB data contract with unlimited calls and unlimited SMS for £28 a month.

O2 themselves offer a £28 contract on the Fire phone, but you only get 500MB data and 500 minutes, so best to go through

On the small sample that we've looked it, it's clear that shopping around is always important and that Amazon isn't going to simply offer you the best deal.

In many cases, the offering looks to match the prices offered by other online retailers, however, but of course Amazon is a familiar brand to many which may well bring with it confidence to shop online that others might lack. Shopping around might bring you alternative deals, so it's always worth a quick comparison elsewhere, for example on the Pocket-lint Phonestore.