Haggle your way to £100 off, the £8 rule and who has the best perks: How to get a better mobile deal

Small mobile network providers have outclassed the big four in a survey of more than 4,000 customers - especially when it comes to value for money.

EE, O2, Three and Vodafone, all of whom are charging annual price rises, were outshone by the likes of Smarty, Voxi and Talkmobile in customer scores collected by Which?. Read all the latest Money news here With that in mind, our Money team joined forces with the consumer champion to produce a guide to getting a good deal - from perks to haggling, roaming charges to annual price hikes.

Here Which?'s head of home products and services Natalie Hitchins gives her top tips... Best perks right now Some of the best perks on the market are the data flexibility and data roaming offered by the smaller providers.

Several providers offer free EU roaming. iD Mobile and Lebara offer 30GB of roaming, Smarty offers 12GB and Talkmobile and Giffgaff both offer 5GB.

At GiffGaff, you can change the data allowance on your 18-month contract as needed - meaning you aren't stuck paying for data you don't need if your circumstances change. Voxi also offers data-free use of social media, video and music streaming apps.

Some providers, like Sky and iD Mobile, also allow you to roll over unused data. This means low data users can opt for a cheap deal and still have the security of top-ups from any data that's gone unused the previous month.

Don't pay more than £8 a month for sim-only contract The biggest mistake most people make is paying more than £8 a month for a sim-only contract. You can get great rolling sim-only deals with plenty of data from smaller providers - like Smarty, Talkmobile and Voxi - for a fraction of the cost of the big four providers.

It's always worth shopping around and checking prices at the smaller providers before you settle on a contract. Another common mistake is paying for more data than you need.

Our research has found that although 17% of people are paying for unlimited data, only 13% of consumers use more than 20GB per month. Check the signal Check what the signal is like in your area before you decide on a network - you can do this using the Ofcom website and by checking the website of the provider you're looking to switch to.

If you're still unsure or want evidence of which is the best, you can just get a one-month sim-only deal with a network and see how it performs, then try a different one next month. Consider second-hand If you're in the market for a new phone and aren't bothered about having the latest model, don't overlook second-hand websites.

Our research shows you can get good savings on a smartphone by looking at the second-hand and refurbished market. Comparison sites or buy direct? Comparison sites can be a really good place to start to get an understanding of what's available and what might be the best deal for you.

The most important decision to make before you start shopping around is whether you'd be better off on a bundled contract with a phone, or a sim-only contract where you use your existing phone, or buy one outright. Which? has a mobile contract calculator you can use to decide which type of contract is best for you.

Can you haggle? Absolutely! Haggling is expected by providers and is a good opportunity to discuss the elements of your deal and upgrade or downgrade if the package doesn't quite fit your needs. Our latest research found that the average mobile customer saved £61 a year by haggling, but this was bested by an average of £58 for both O2 and Vodafone customers and a startlingly high £101 for EE customers.

Mid-contract price hikes Look out for any annual price rises included in the contract. For sim-only contracts with the big four providers - EE, O2, Three and Vodafone - customers will see their bill increase by £1 to £1.80 a month from this month and for those on bundled contracts with EE, costs will increase by £4 a month.

Most smaller providers do not impose mid-contract price hikes so Which? would recommend choosing one of these over the big four for a cheap, flexible sim-only deal. You should also check what the extra charges are if you use more than your texts, calls or data allowance.

Read more:'I paid a builder £500 and they ghosted me'How to complain in a restaurantBritish passports have just got more expensive Exit fees and contract length Importantly, make sure you know how long a contract lasts - typically it'll be 24 months, 12 or one month. If your contract is longer than one month, check what the exit fees are if you need to get out of the contract early - this helps to ensure you don't encounter any nasty surprises down the road.

Choosing a rolling one-month contract will give you flexibility if you want to switch to a different provider. Roaming charges It's also worth looking out for details of any roaming charges when you join as some networks will charge you to send texts, make calls and use data abroad.

Smaller providers often allow you to use your data, calls and texts allowance for free in Europe with no additional charges..