There is currently a myriad of suppliers offering a bewildering array of deals. Price comparison websites don't seem to make it any easier. It can also be hard to change suppliers. Check your existing contracts for termination provisions; some suppliers provide only a short window in which you can give notice. So keep an eye out or you could be tied into a contract for at least another year.
Scrutinise your telephone bills carefully for a host of potential cost savings. Are you paying for a call that lasts just two seconds because you're paying a connection charge? You shouldn't be. Are you paying more than 10p a minute to call a mobile phone number? You shouldn't be. Do you have a deal that seems great because it gives you loads of free minutes? If you're not using them all, it isn't such a great deal.