How can I get a better deal on my landline / broadband?

The MoneyHelper website offers the following tips:

Switch supplier. Sticking with the same broadband and home phone provider can be expensive.
Match your deal to your needs. If you're not sure how much you use, ask your supplier.
Pay by direct debit. It's usually the cheapest way to pay and it means you won't forget.
Avoid peak calling times. Check when your supplier charges most for calls and do your best to avoid these times.
Use more than one comparison website to compare tariffs, such as:

Social Tariffs

If you are claiming certain benefits, you may be able to get a monthly broadband deal at a reduced price. Some providers offer bespoke deals, known as 'social tariffs', at much lower prices. BT Home Essentials (detailed below) is an example of this.

Social tariffs are discounted broadband packages available for people who are in receipt of certain benefits such as Universal Credit, Pension Credit, Jobseeker’s Allowance or Income Support. They’re still usually the same speed and quality as other home broadband deals, the only difference is the price.

Find out more:

Uswitch, the comparison and switching service, has information about how to get a social tariff on universal credit.
Ofcom, the communications regulator, has an up-to-date list of providers who offer social tariffs and eligibility criteria.